I've just started a GIS position at a state agency in Illinois, and my newbie status is about to come out by asking the following:
How do residents living outside of incorporated areas determine their 'City' address? I thought that it was based on the township that their residence is located in, but it looks like townships and other county subdivisions are only governmental boundaries, and not boundaries that are recognized by USPS. For example, a resident residing outside of a municipality but within the township of Prairie Du Long actually lives at xxxx Klein Rd., Smithton, IL, not xxxx Klein Rd., Prairie Du Long, IL.
So how does the USPS determine the 'City' of a rural address? Is it based on the zip code of the address? Is there a map (or better yet, a shapefile) that displays the 'City' boundaries in a particular state? I realize this may ultimately be a question that should posed to USPS, but I figured I'd start with this forum.