This guide to census geographies may be illuminating. The Census Bureau has multiple levels of fallback statistical areas when a given jurisdiction isn’t completely subdivided like its neighbors. The relationship between census geographies can be complex, but for the purpose of this discussion, it boils down to these summary levels, which correspond to admin_level=* values:
admin_level=* |
Census summary level | General administrative geography | Equivalent census geographies |
|---|---|---|---|
| 6 | County equivalent | County (borough in Alaska) | Census Area (in Alaska) |
| 7 | County subdivision | Minor Civil Division (in 29 states, e.g., township) | Census County Division (in 20 states), Census Subarea (in Alaska), Unorganized Territory (in 9 states) |
| 8 | Place | Incorporated Place (e.g., city) | Census Designated Place |
In principle, census geographies are defined solely for statistical purposes; their boundaries are more arbitrary than administrative geographies. However, some of the census geographies have taken on more meaning through happenstance or (mis)use. CDPs are usually named after real unincorporated places that lack boundaries, so people and datasets often conflate the two. I could buy that people routinely use Alaska’s census areas wherever they need a county equivalent instead of special-casing Alaska’s Unorganized Borough, just as they don’t want to leave a hole in Connecticut because that state refuses to be divided into counties. But most states’ minor civil divisions are somewhat obscure by comparison to counties and incorporated places, so UTs and CCDs are that much more obscure.
In other words, you did the right thing by tagging the Central Pennington Unorganized Territory as boundary=census rather than boundary=administrative. At least it’s consistent with Maine. But as to whether you should bother mapping out all the rest of South Dakota’s unorganized territories or delete the ones you’ve mapped, it comes down to whether the local community cares to maintain this information. It’s not all that difficult to keep up with changes to Alaska’s dozen census areas, whereas CCDs/UTs and CDPs are much more numerous. The combination of obscurity and number makes CCDs/UTs not a great tradeoff in my opinion. 