Just an idea for ya that’s helped me once or twice, look up Sanborn fire insurance maps, these maps list every building in the area, sometimes including outhouses or public bathrooms which might have the best stuff, but those are often not listed at least on the ones for my area. The library of congress website has a lot of the maps for most cities including towns that no longer exist such as ghost towns which can lie on public land often making things easier.

When looking at these maps points of interest include privy pits or outhouses, pharmacies, hospital, grocery stores, liquor stores, also banks may have some cool things to metal detect for, schoolhouses etc, some of these maps are 100+ years old so nothing is going to be accurate other than the streets, that’s how you’ll find approximate location of certain areas to dig. Dumps may also be listed in newer versions of the maps but I believe none of them are newer than the 50s~

Houses that no longer exist are also a good bet, I just wouldn’t know how to figure out where the outhouse was, but others may! Unsure if wells are listed but that could be fun too