Roi Qualls writes:
Attached is the list that I use. (mwsCounties.csv)
Strictly speaking clusters are not defined by county, but rather by locality. That is, localities never span clusters. This is relevant in urban areas. For example, OH-03 (Franklin County / Columbus) includes all of Westerville, including the part that goes into Delaware County. OH-05 (Hamilton Cty / Cinci) includes a township in Indiana. At the scale that we typically publish maps these are negligible considerations. If we start doing cluster level maps it becomes more relevant. That being said, all of the maps that I have done are at the county level.
I have attached a spreadsheet of the county – cluster relationship in IN, OH, MI. I believe this is still current. We should check to make sure the list reflects the update to one of the counties in N. MI which was changed to a different cluster.
I followed these instructions to add a layer to the map highlighting Michigain, Ohio, and Indiana — using the file Admin 1 — States, Provinces (without large lakes) instead of Admin 0 — Countries.