diff --git a/environment-dev.yml b/environment-dev.yml
index 5dc1482f..189f494b 100644
--- a/environment-dev.yml
+++ b/environment-dev.yml
@@ -26,6 +26,7 @@ dependencies:
   - netcdf4
   - numpy>=1.25
   - pandas>=2.0
+  - polars>=1.0
   - pygrib>=2.1.4
   - pylint
   - pyproj>=3.6
diff --git a/herbie/__init__.py b/herbie/__init__.py
index 0231793b..07277612 100644
--- a/herbie/__init__.py
+++ b/herbie/__init__.py
@@ -42,7 +42,7 @@
     ## TODO: Will the `_version.py` file *always* be present?
     ## TODO: What if the person doesn't do "pip install"
     from ._version import __version__, __version_tuple__
-except:
+except Exception:
     __version__ = "unknown"
     __version_tuple__ = (999, 999, 999)
 
@@ -50,7 +50,7 @@
 ########################################################################
 # Overload Path object with my custom `expand` method so the user can
 # set environment variables in the config file (e.g., ${HOME}).
-def _expand(self, resolve=False, absolute=False):
+def _expand(self, resolve: bool = False, absolute: bool = False) -> Path:
     """
     Fully expand the Path with the given environment variables.
 
@@ -149,7 +149,7 @@ def template(self):
 try:
     # Load the Herbie config file
     config = toml.load(_config_file)
-except:
+except Exception:
     try:
         # Create the Herbie config file
         _config_path.mkdir(parents=True, exist_ok=True)
diff --git a/herbie/accessors.py b/herbie/accessors.py
index 12879b98..f8f0f4eb 100644
--- a/herbie/accessors.py
+++ b/herbie/accessors.py
@@ -14,6 +14,7 @@
 import re
 import warnings
 from pathlib import Path
+from typing import Literal, Optional, Union
 
 import numpy as np
 import pandas as pd
@@ -23,7 +24,6 @@
 
 import herbie
 
-
 _level_units = dict(
     adiabaticCondensation="adiabatic condensation",
     atmosphere="atmosphere",
@@ -54,7 +54,7 @@
 )
 
 
-def add_proj_info(ds):
+def add_proj_info(ds: xr.Dataset):
     """Add projection info to a Dataset."""
     match = re.search(r'"source": "(.*?)"', ds.history)
     FILE = Path(match.group(1))
@@ -97,7 +97,7 @@ def __init__(self, xarray_obj):
         self._center = None
 
     @property
-    def center(self):
+    def center(self) -> tuple[float, float]:
         """Return the geographic center point of this dataset."""
         if self._center is None:
             # we can use a cache on our accessor objects, because accessors
@@ -107,19 +107,18 @@ def center(self):
             self._center = (float(lon.mean()), float(lat.mean()))
         return self._center
 
-    def to_180(self):
+    def to_180(self) -> xr.Dataset:
         """Wrap longitude coordinates as range [-180,180]."""
         ds = self._obj
         ds["longitude"] = (ds["longitude"] + 180) % 360 - 180
         return ds
 
-    def to_360(self):
+    def to_360(self) -> xr.Dataset:
         """Wrap longitude coordinates as range [0,360]."""
         ds = self._obj
         ds["longitude"] = (ds["longitude"] - 360) % 360
         return ds
 
-
     @functools.cached_property
     def crs(self):
         """
@@ -196,7 +195,9 @@ def polygon(self):
 
         return domain_polygon, domain_polygon_latlon
 
-    def with_wind(self, which="both"):
+    def with_wind(
+        self, which: Literal["both", "speed", "direction"] = "both"
+    ) -> xr.Dataset:
         """Return Dataset with calculated wind speed and/or direction.
 
         Consistent with the eccodes GRIB parameter database, variables
@@ -228,7 +229,7 @@ def with_wind(self, which="both"):
                 ds["si10"].attrs["standard_name"] = "wind_speed"
                 ds["si10"].attrs["grid_mapping"] = ds.u10.attrs.get("grid_mapping")
                 n_computed += 1
-            
+
             if {"u100", "v100"}.issubset(ds):
                 ds["si100"] = np.sqrt(ds.u100**2 + ds.v100**2)
                 ds["si100"].attrs["GRIB_paramId"] = 228249
@@ -237,7 +238,7 @@ def with_wind(self, which="both"):
                 ds["si100"].attrs["standard_name"] = "wind_speed"
                 ds["si100"].attrs["grid_mapping"] = ds.u100.attrs.get("grid_mapping")
                 n_computed += 1
-            
+
             if {"u80", "v80"}.issubset(ds):
                 ds["si80"] = np.sqrt(ds.u80**2 + ds.v80**2)
                 ds["si80"].attrs["long_name"] = "80 metre wind speed"
@@ -266,7 +267,7 @@ def with_wind(self, which="both"):
                 ds["wdir10"].attrs["standard_name"] = "wind_from_direction"
                 ds["wdir10"].attrs["grid_mapping"] = ds.u10.attrs.get("grid_mapping")
                 n_computed += 1
-            
+
             if {"u100", "v100"}.issubset(ds):
                 ds["wdir100"] = (
                     (270 - np.rad2deg(np.arctan2(ds.v100, ds.u100))) % 360
@@ -276,7 +277,7 @@ def with_wind(self, which="both"):
                 ds["wdir100"].attrs["standard_name"] = "wind_from_direction"
                 ds["wdir100"].attrs["grid_mapping"] = ds.u100.attrs.get("grid_mapping")
                 n_computed += 1
-            
+
             if {"u80", "v80"}.issubset(ds):
                 ds["wdir80"] = (
                     (270 - np.rad2deg(np.arctan2(ds.v80, ds.u80))) % 360
@@ -305,15 +306,15 @@ def with_wind(self, which="both"):
 
     def pick_points(
         self,
-        points,
-        method="nearest",
+        points: pd.DataFrame,
+        method: Literal["nearest", "weighted"] = "nearest",
         *,
-        k=None,
-        max_distance=500,
-        use_cached_tree=True,
-        tree_name=None,
-        verbose=False,
-    ):
+        k: Optional[int] = None,
+        max_distance: Union[int, float] = 500,
+        use_cached_tree: Union[bool, Literal["replant"]] = True,
+        tree_name: Optional[str] = None,
+        verbose: bool = False,
+    ) -> xr.Dataset:
         """Pick nearest neighbor grid values at selected  points.
 
         Parameters
@@ -384,7 +385,7 @@ def pick_points(
                 "`pip install 'herbie-data[extras]'` for the full functionality."
             )
 
-        def plant_tree(save_pickle=None):
+        def plant_tree(save_pickle: Optional[Union[Path, str]] = None):
             """Grow a new BallTree object from seedling."""
             timer = pd.Timestamp("now")
             print("INFO: 🌱 Growing new BallTree...", end="")
@@ -719,9 +720,10 @@ def plot(self, ax=None, common_features_kw={}, vars=None, **kwargs):
         raise NotImplementedError("Plotting functionality is not working right now.")
 
         try:
-            from herbie.toolbox import EasyMap, pc
-            from herbie import paint
             import matplotlib.pyplot as plt
+
+            from herbie import paint
+            from herbie.toolbox import EasyMap, pc
         except ModuleNotFoundError:
             raise ModuleNotFoundError(
                 "cartopy is an 'extra' requirement. Please use "
diff --git a/herbie/core.py b/herbie/core.py
index 4f0d6130..fd5375c0 100644
--- a/herbie/core.py
+++ b/herbie/core.py
@@ -18,6 +18,7 @@
 from datetime import datetime, timedelta
 from io import StringIO
 from shutil import which
+from typing import Union, Optional, Literal
 
 import cfgrib
 import pandas as pd
@@ -31,6 +32,8 @@
 from herbie.help import _search_help
 from herbie.misc import ANSI
 
+Datetime = Union[datetime, pd.Timestamp, str]
+
 # NOTE: The config dict values are retrieved from __init__ and read
 # from the file ${HOME}/.config/herbie/config.toml
 # Path is imported from __init__ because it has my custom methods.
@@ -59,7 +62,7 @@
     )
 
 
-def wgrib2_idx(grib2filepath):
+def wgrib2_idx(grib2filepath: Union[Path, str]) -> str:
     """
     Produce the GRIB2 inventory index with wgrib2.
 
@@ -81,7 +84,7 @@ def wgrib2_idx(grib2filepath):
         raise RuntimeError("wgrib2 command was not found.")
 
 
-def create_index_files(path, overwrite=False):
+def create_index_files(path: Union[Path, str], overwrite: bool = False) -> None:
     """Create an index file for all GRIB2 files in a directory.
 
     Parameters
@@ -91,7 +94,7 @@ def create_index_files(path, overwrite=False):
     overwrite : bool
         Overwrite index file if it exists.
     """
-    path = Path(path).expand()
+    path = Path(path)
     files = []
     if path.is_dir():
         # List all GRIB2 files in the directory
@@ -168,16 +171,16 @@ class Herbie:
 
     def __init__(
         self,
-        date=None,
+        date: Optional[Datetime] = None,
         *,
-        valid_date=None,
-        model=config["default"].get("model"),
-        fxx=config["default"].get("fxx"),
-        product=config["default"].get("product"),
-        priority=config["default"].get("priority"),
-        save_dir=config["default"].get("save_dir"),
-        overwrite=config["default"].get("overwrite", False),
-        verbose=config["default"].get("verbose", True),
+        valid_date: Optional[Datetime] = None,
+        model: str = config["default"].get("model"),
+        fxx: int = config["default"].get("fxx"),
+        product: str = config["default"].get("product"),
+        priority: Union[str, list[str]] = config["default"].get("priority"),
+        save_dir: Union[Path, str] = config["default"].get("save_dir"),
+        overwrite: bool = config["default"].get("overwrite", False),
+        verbose: bool = config["default"].get("verbose", True),
         **kwargs,
     ):
         """Specify model output and find GRIB2 file at one of the sources."""
@@ -282,7 +285,7 @@ def __init__(
                     f"┊ {ANSI.green}{self.date:%Y-%b-%d %H:%M UTC}{ANSI.bright_green} F{self.fxx:02d}{ANSI.reset}",
                 )
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         """Representation in Notebook."""
         msg = (
             f"{ANSI.herbie} {self.model.upper()} model",
@@ -292,17 +295,17 @@ def __repr__(self):
         )
         return " ".join(msg)
 
-    def __str__(self):
+    def __str__(self) -> str:
         """When Herbie class object is printed, print all properties."""
         # * Keep this simple so it runs fast.
         msg = (f"║HERBIE╠ {self.model.upper()}:{self.product}",)
         return " ".join(msg)
 
-    def __bool__(self):
+    def __bool__(self) -> bool:
         """Herbie evaluated True if the GRIB file exists."""
         return bool(self.grib)
 
-    def help(self):
+    def help(self) -> None:
         """Print help message if available."""
         if hasattr(self, "HELP"):
             HELP = self.HELP.strip().replace("\n", "\n│ ")
@@ -319,7 +322,7 @@ def help(self):
         print("│")
         print("╰─────────────────────────────────────────")
 
-    def tell_me_everything(self):
+    def tell_me_everything(self) -> None:
         """Print all the attributes of the Herbie object."""
         msg = []
         for i in dir(self):
@@ -329,11 +332,11 @@ def tell_me_everything(self):
         msg = "\n".join(msg)
         print(msg)
 
-    def __logo__(self):
+    def __logo__(self) -> None:
         """For Fun, show the Herbie Logo."""
         print(ANSI.ascii)
 
-    def _validate(self):
+    def _validate(self) -> None:
         """Validate the Herbie class input arguments."""
         # Accept model alias
         if self.model.lower() == "alaska":
@@ -367,7 +370,7 @@ def _validate(self):
                 if self.date < expired:
                     self.priority.remove("nomads")
 
-    def _ping_pando(self):
+    def _ping_pando(self) -> None:
         """Pinging the Pando server before downloading can prevent a bad handshake."""
         try:
             requests.head("https://pando-rgw01.chpc.utah.edu/")
@@ -375,7 +378,7 @@ def _ping_pando(self):
             print("🤝🏻⛔ Bad handshake with pando? Am I able to move on?")
             pass
 
-    def _check_grib(self, url, min_content_length=10):
+    def _check_grib(self, url: str, min_content_length: int = 10) -> bool:
         """
         Check that the GRIB2 URL exist and is of useful length.
 
@@ -398,7 +401,7 @@ def _check_grib(self, url, min_content_length=10):
         else:
             return False
 
-    def _check_idx(self, url, verbose=False):
+    def _check_idx(self, url: str, verbose: bool = False) -> tuple[bool, Optional[str]]:
         """Check if an index file exist for the GRIB2 URL."""
         # To check inventory files with slightly different URL structure
         # we will loop through the IDX_SUFFIX.
@@ -427,7 +430,7 @@ def _check_idx(self, url, verbose=False):
             )
         return False, None
 
-    def find_grib(self):
+    def find_grib(self) -> tuple[Optional[Union[Path, str]], Optional[str]]:
         """Find a GRIB file from the archive sources.
 
         Returns
@@ -465,15 +468,15 @@ def find_grib(self):
             grib_url = self.SOURCES[source]
 
             if source.startswith("local"):
-                grib_path = Path(grib_url).expand()
+                grib_path = Path(grib_url)
                 if grib_path.exists():
-                    return [grib_path, source]
+                    return (grib_path, source)
             elif self._check_grib(grib_url):
-                return [grib_url, source]
+                return (grib_url, source)
 
-        return [None, None]
+        return (None, None)
 
-    def find_idx(self):
+    def find_idx(self) -> tuple[Optional[Union[Path, str]], Optional[str]]:
         """Find an index file for the GRIB file."""
         # If priority list is set, we want to search SOURCES in that
         # priority order. If priority is None, then search all SOURCES
@@ -498,33 +501,35 @@ def find_idx(self):
             grib_url = self.SOURCES[source]
 
             if source.startswith("local"):
-                local_grib = Path(grib_url).expand()
+                local_grib = Path(grib_url)
                 local_idx = local_grib.with_suffix(self.IDX_SUFFIX[0])
                 if local_idx.exists():
-                    return [local_idx, "local"]
+                    return (local_idx, "local")
             else:
                 idx_exists, idx_url = self._check_idx(grib_url)
 
                 if idx_exists:
-                    return [idx_url, source]
+                    return (idx_url, source)
 
-        return [None, None]
+        return (None, None)
 
     @property
-    def get_remoteFileName(self, source=None):
+    def get_remoteFileName(self, source: Optional[str] = None) -> str:
         """Predict remote file name (assumes all sources are named the same)."""
         if source is None:
             source = list(self.SOURCES)[0]
         return self.SOURCES[source].split("/")[-1]
 
     @property
-    def get_localFileName(self):
+    def get_localFileName(self) -> str:
         """Predict the local file name."""
         return self.LOCALFILE
 
-    def get_localFilePath(self, search=None, *, searchString=None):
+    def get_localFilePath(
+        self, search: Optional[str] = None, *, searchString=None
+    ) -> Path:
         """Get full path to the local file."""
-        # TODO: Remove this eventually
+        # TODO: Remove this check for searString eventually
         if searchString is not None:
             warnings.warn(
                 "The argument `searchString` was renamed `search`. Please update your scripts.",
@@ -535,10 +540,7 @@ def get_localFilePath(self, search=None, *, searchString=None):
 
         # Predict the localFileName from the first model template SOURCE.
         localFilePath = (
-            self.save_dir.expand()
-            / self.model
-            / f"{self.date:%Y%m%d}"
-            / self.get_localFileName
+            self.save_dir / self.model / f"{self.date:%Y%m%d}" / self.get_localFileName
         )
 
         # Check if any sources in a model template are "local"
@@ -546,9 +548,9 @@ def get_localFilePath(self, search=None, *, searchString=None):
         if any([i.startswith("local") for i in self.SOURCES.keys()]):
             localFilePath = next(
                 (
-                    Path(self.SOURCES[i]).expand()
+                    Path(self.SOURCES[i])
                     for i in self.SOURCES
-                    if i.startswith("local") and Path(self.SOURCES[i]).expand().exists()
+                    if i.startswith("local") and Path(self.SOURCES[i]).exists()
                 ),
                 localFilePath,
             )
@@ -595,7 +597,7 @@ def get_localFilePath(self, search=None, *, searchString=None):
         return localFilePath
 
     @functools.cached_property
-    def index_as_dataframe(self):
+    def index_as_dataframe(self) -> pd.DataFrame:
         """Read and cache the full index file."""
         if self.grib_source == "local" and wgrib2:
             # Generate IDX inventory with wgrib2
@@ -762,7 +764,13 @@ def index_as_dataframe(self):
 
         return df
 
-    def inventory(self, search=None, *, searchString=None, verbose=None):
+    def inventory(
+        self,
+        search: Optional[str] = None,
+        *,
+        searchString=None,
+        verbose: Optional[bool] = None,
+    ) -> pd.DataFrame:
         """
         Inspect the GRIB2 file contents by reading the index file.
 
@@ -817,15 +825,15 @@ def inventory(self, search=None, *, searchString=None, verbose=None):
 
     def download(
         self,
-        search=None,
+        search: Optional[str] = None,
         *,
         searchString=None,
-        source=None,
-        save_dir=None,
-        overwrite=None,
-        verbose=None,
-        errors="warn",
-    ):
+        source: Optional[str] = None,
+        save_dir: Optional[Union[str, Path]] = None,
+        overwrite: Optional[bool] = None,
+        verbose: Optional[bool] = None,
+        errors: Literal["warn", "raise"] = "warn",
+    ) -> Path:
         """
         Download file from source.
 
@@ -1048,13 +1056,13 @@ def subset(search, outFile):
 
     def xarray(
         self,
-        search=None,
+        search: Optional[str] = None,
         *,
         searchString=None,
-        backend_kwargs={},
-        remove_grib=True,
+        backend_kwargs: dict = {},
+        remove_grib: bool = True,
         **download_kwargs,
-    ):
+    ) -> xr.Dataset:
         """
         Open GRIB2 data as xarray DataSet.
 
@@ -1188,7 +1196,7 @@ def xarray(
                     )
             return Hxr
 
-    def terrain(self, water_masked=True):
+    def terrain(self, water_masked: bool = True) -> xr.Dataset:
         """Shortcut method to return model terrain as an xarray.Dataset."""
         ds = self.xarray(":(?:HGT|LAND):surface")
         if water_masked:
diff --git a/herbie/fast.py b/herbie/fast.py
index fa638944..c0aa6cda 100644
--- a/herbie/fast.py
+++ b/herbie/fast.py
@@ -8,9 +8,10 @@
 """
 
 import logging
-
-# Multithreading :)
 from concurrent.futures import ThreadPoolExecutor, as_completed
+from datetime import datetime
+from typing import Union, Optional
+from pathlib import Path
 
 import pandas as pd
 import xarray as xr
@@ -19,6 +20,7 @@
 
 log = logging.getLogger(__name__)
 
+Datetime = Union[datetime, pd.Timestamp, str]
 
 """
 🧵🤹🏻‍♂️ Notice! Multithreading and Multiprocessing is use
@@ -30,8 +32,8 @@
 """
 
 
-def _validate_fxx(fxx):
-    """Fast Herbie requires fxx as a list-like"""
+def _validate_fxx(fxx: Union[int, Union[list[int], range]]) -> Union[list[int], range]:
+    """Fast Herbie requires fxx as a list-like."""
     if isinstance(fxx, int):
         fxx = [fxx]
 
@@ -41,8 +43,8 @@ def _validate_fxx(fxx):
     return fxx
 
 
-def _validate_DATES(DATES):
-    """Fast Herbie requires DATES as a list-like"""
+def _validate_DATES(DATES: Union[Datetime, list[Datetime]]) -> list[Datetime]:
+    """Fast Herbie requires DATES as a list-like."""
     if isinstance(DATES, str):
         DATES = [pd.to_datetime(DATES)]
     elif not hasattr(DATES, "__len__"):
@@ -56,7 +58,7 @@ def _validate_DATES(DATES):
     return DATES
 
 
-def Herbie_latest(n=6, freq="1h", **kwargs):
+def Herbie_latest(n: int = 6, freq: str = "1h", **kwargs) -> Herbie:
     """Search for the most recent GRIB2 file (using multithreading).
 
     Parameters
@@ -85,7 +87,16 @@ def Herbie_latest(n=6, freq="1h", **kwargs):
 
 
 class FastHerbie:
-    def __init__(self, DATES, fxx=[0], *, max_threads=50, **kwargs):
+    """Create many Herbie objects quickly."""
+
+    def __init__(
+        self,
+        DATES: Union[Datetime, list[Datetime]],
+        fxx: Union[int, list[int]] = [0],
+        *,
+        max_threads: int = 50,
+        **kwargs,
+    ):
         """Create many Herbie objects with methods to download or read with xarray.
 
         Uses multithreading.
@@ -156,10 +167,11 @@ def __init__(self, DATES, fxx=[0], *, max_threads=50, **kwargs):
                 f"Could not find {len(self.file_not_exists)}/{len(self.file_exists)} GRIB files."
             )
 
-    def __len__(self):
+    def __len__(self) -> int:
+        """Return the number of Herbie objects."""
         return len(self.objects)
 
-    def df(self):
+    def df(self) -> pd.DataFrame:
         """Organize Herbie objects into a DataFrame.
 
         #? Why is this inefficient? Takes several seconds to display because the __str__ does a lot.
@@ -172,7 +184,7 @@ def df(self):
             ds_list, index=self.DATES, columns=[f"F{i:02d}" for i in self.fxx]
         )
 
-    def inventory(self, search=None):
+    def inventory(self, search: Optional[str] = None):
         """Get combined inventory DataFrame.
 
         Useful for data discovery and checking your search before
@@ -186,8 +198,10 @@ def inventory(self, search=None):
             dfs.append(df)
         return pd.concat(dfs, ignore_index=True)
 
-    def download(self, search=None, *, max_threads=20, **download_kwargs):
-        r"""Download many Herbie objects
+    def download(
+        self, search: Optional[str] = None, *, max_threads: int = 20, **download_kwargs
+    ) -> list[Path]:
+        r"""Download many Herbie objects.
 
         Uses multithreading.
 
@@ -231,11 +245,11 @@ def download(self, search=None, *, max_threads=20, **download_kwargs):
 
     def xarray(
         self,
-        search,
+        search: Optional[str],
         *,
-        max_threads=None,
+        max_threads: Optional[int] = None,
         **xarray_kwargs,
-    ):
+    ) -> xr.Dataset:
         """Read many Herbie objects into an xarray Dataset.
 
         # TODO: Sometimes the Jupyter Cell always crashes when I run this.
@@ -302,7 +316,7 @@ def xarray(
                 concat_dim=["time", "step"],
                 combine_attrs="drop_conflicts",
             )
-        except:
+        except Exception:
             # TODO: I'm not sure why some cases doesn't like the combine_attrs argument
             ds = xr.combine_nested(
                 ds_list,
diff --git a/herbie/toolbox/cartopy_tools.py b/herbie/toolbox/cartopy_tools.py
index 5bce2dc6..b386ced2 100644
--- a/herbie/toolbox/cartopy_tools.py
+++ b/herbie/toolbox/cartopy_tools.py
@@ -36,6 +36,7 @@
 from metpy.plots import USCOUNTIES
 from mpl_toolkits.axes_grid1.inset_locator import InsetPosition
 
+from typing import Literal, Optional, Union
 from herbie import Path
 
 try:
@@ -46,6 +47,8 @@
     # )
     pass
 
+type ExtentPadding = Union[Literal["auto"], float, dict[str, float]]
+
 pc = ccrs.PlateCarree()
 pc._threshold = 0.01  # https://github.com/SciTools/cartopy/issues/8
 
@@ -88,7 +91,12 @@ def to_360(lon):
 
 ########################################################################
 # Methods attached to axes created by `EasyMap`
-def _adjust_extent(self, pad="auto", fraction=0.05, verbose=False):
+def _adjust_extent(
+    self,
+    pad: ExtentPadding = "auto",
+    fraction: float = 0.05,
+    verbose: bool = False,
+):
     """
     Adjust the extent of an existing cartopy axes.
 
@@ -147,13 +155,13 @@ def _adjust_extent(self, pad="auto", fraction=0.05, verbose=False):
 
 def _center_extent(
     self,
-    lon=None,
-    lat=None,
-    city=None,
-    state=None,
+    lon: Optional[Union[int, float]] = None,
+    lat: Optional[Union[int, float]] = None,
+    city: Optional[str] = None,
+    state: Optional[str] = None,
     *,
-    pad="auto",
-    verbose=False,
+    pad: ExtentPadding = "auto",
+    verbose: bool = False,
 ):
     """
     Change the map extent to be centered on a point and adjust padding.
@@ -251,7 +259,9 @@ def _copy_extent(self, src_ax):
 
 ########################################################################
 # Main Functions
-def check_cartopy_axes(ax=None, crs=pc, *, fignum=None, verbose=False):
+def check_cartopy_axes(
+    ax=None, crs=pc, *, fignum: Optional[int] = None, verbose: bool = False
+):
     """
     Check if an axes is a cartopy axes, else create a new cartopy axes.
 
@@ -299,7 +309,11 @@ def check_cartopy_axes(ax=None, crs=pc, *, fignum=None, verbose=False):
             raise TypeError("🌎 Sorry. The `ax` you gave me is not a cartopy axes.")
 
 
-def get_ETOPO1(top="ice", coarsen=None, thin=None):
+def get_ETOPO1(
+    top: Literal["bedrock", "ice"] = "ice",
+    coarsen: Optional[int] = None,
+    thin: Optional[int] = None,
+):
     """
     Return the ETOPO1 elevation and bathymetry DataArray.
 
@@ -381,12 +395,12 @@ def _reporthook(a, b, c):
 
 def inset_global_map(
     ax,
-    x=0.95,
-    y=0.95,
-    size=0.3,
-    theme=None,
-    facecolor="#f88d0083",
-    kind="area",
+    x: float = 0.95,
+    y: float = 0.95,
+    size: float = 0.3,
+    theme: Optional[Literal["dark", "grey"]] = None,
+    facecolor: str = "#f88d0083",
+    kind: Literal["point", "area"] = "area",
 ):
     """Add an inset map showing the location of the main map on the globe.
 
@@ -478,7 +492,12 @@ def inset_global_map(
     return ax_inset
 
 
-def state_polygon(state=None, country="USA", county=None, verbose=True):
+def state_polygon(
+    state: Optional[str] = None,
+    country: str = "USA",
+    county: Optional[str] = None,
+    verbose: bool = True,
+):
     """
     Return a shapely polygon of US state boundaries or country borders.
 
@@ -528,18 +547,18 @@ class EasyMap:
 
     def __init__(
         self,
-        scale="110m",
+        scale: Literal["110m", "50m", "10m"] = "110m",
         ax=None,
         crs=pc,
         *,
         figsize=None,
-        fignum=None,
-        dpi=None,
-        theme=None,
-        verbose=False,
-        add_coastlines=True,
-        facecolor=None,
+        fignum: int = None,
+        dpi: int = None,
+        theme: Optional[Literal["dark", "grey"]] = None,
+        add_coastlines: bool = True,
+        facecolor: Optional[str] = None,
         coastlines_kw={},
+        verbose: bool = False,
         **kwargs,
     ):
         """
@@ -804,10 +823,10 @@ def LAKES(self, **kwargs):
     # Less commonly needed features
     def TERRAIN(
         self,
-        coarsen=30,
+        coarsen: int = 30,
         *,
-        top="ice",
-        kind="pcolormesh",
+        top: Literal["ice", "bedrock"] = "ice",
+        kind: Literal["pcolormesh", "contourf"] = "pcolormesh",
         extent=None,
         **kwargs,
     ):
@@ -885,10 +904,10 @@ def TERRAIN(
 
     def BATHYMETRY(
         self,
-        coarsen=30,
+        coarsen: int = 30,
         *,
-        top="ice",
-        kind="pcolormesh",
+        top: Literal["ice", "bedrock"] = "ice",
+        kind: Literal["pcolormesh", "contourf"] = "pcolormesh",
         extent=None,
         **kwargs,
     ):
@@ -1044,10 +1063,10 @@ def ROADS(self, road_types=None, **kwargs):
 
     def PLACES(
         self,
-        country="United States",
-        rank=2,
-        scatter=True,
-        labels=True,
+        country: str = "United States",
+        rank: int = 2,
+        scatter: bool = True,
+        labels: bool = True,
         label_kw={},
         scatter_kw={},
     ):
@@ -1090,7 +1109,14 @@ def PLACES(
 
     # ============
     # Tiled images
-    def STAMEN(self, style="terrain-background", zoom=3, alpha=1):
+    def STAMEN(
+        self,
+        style: Literal[
+            "terrain-background", "terrain", "toner-background", "toner", "watercolor"
+        ] = "terrain-background",
+        zoom: int = 3,
+        alpha=1,
+    ):
         """
         Add Stamen map tiles to background.
 
@@ -1139,7 +1165,7 @@ def STAMEN(self, style="terrain-background", zoom=3, alpha=1):
 
         return self
 
-    def OSM(self, zoom=1, alpha=1):
+    def OSM(self, zoom: int = 1, alpha=1):
         """
         Add Open Street Map tiles as background image.
 
@@ -1187,9 +1213,9 @@ def DOMAIN(
         x,
         y=None,
         *,
-        text=None,
-        method="cutout",
-        facealpha=0.25,
+        text: Optional[str] = None,
+        method: Literal["fill", "cutout", "border"] = "cutout",
+        facealpha: Union[Literal[0], Literal[1], float] = 0.25,
         text_kwargs={},
         **kwargs,
     ):