a historical society is a good start. In Maryland and Calvert county we have pretty good records of land ownership online. a little searching and I can get old land deeds. look for old Inns in you area most of them date really far back. I really like just driving around and scouting the area. I find it really cool just driving and noticing a old house tucked away in the woods.
Yep, in Minnesota i logged on to the historical society and they have a good selection. But, I am finding looking at any maps and figuring out what I would do and how long it took to get from point a to point b works and where people of x era would camp helps me pick river crossings, etc., better..
I found old maps on the walls of the local library. Found a muster field, old school house, the location of an old golf course, the old court house, and a change in the road leading into town. Try there, maybe you'll be lucky like I was. HH
If you want some really old maps check out the Library of Congress Map room, on line. It is not easy to navigate, but has a wealth of information. Frank
Check a university's library that is in your state for old Sanborn maps, preferrably if they are online. Example, the University of Texas library has all the Sanborn maps online for Texas cities, and it's free.