Devon’s Hecla Mine thread made me realize that maybe many of you don’t know about the Sanborn maps. The Wikipedia page (Sanborn maps - Wikipedia) provides a good history of them and what they were used for.
For us modelers, they are an invaluable resource for both building locations and size, and track layout.
Take, for example, this map of Canal Street in Philadelphia.
It shows all the trackwork, and all the buildings, both in location and size.
The site takes a bit getting used to in order to navigate, but there’s a ton of valuable information in them.