I just heard about these Sanborn maps from Jayne at The Kelly House. Founded in 1867 by D. A. Sanborn, the Sanborn Map Company was the primary American publisher of fire insurance maps for nearly 100 years. You can see if your house is listed by going to Sanborn Maps. (After you click on the Browse Maps button, you'll need to type in Sanborn for the Username and Welcome for the password.)
I found our house on the 1894 map but missing from the 1888, which makes the house a little younger than I originally thought. We were told when we bought the house that it was built in the 1870's.
The interesting thing was seeing the current footprint of the house on the map. The back "wing" of the house feels like an addition although the basement wall layout supports the idea it was an original section. Seeing this "wing" on the 1894 maps confirms it was original to the house.
I think the "1 1/2" marks on the middle and back wing mean it was a 1 story with a crawl space. They are both 2 stories now, but it feels very cobbed together. Also, it looks like there might have been a front porch in the middle-section of the house. Which is something I wish we still had.
These maps are interesting to look at since you can see the businesses that were operating at that time as well as the fact that there used to be several schools on School Street. There was a cabinet maker, a shoe repair and even the "Home for Old Ladies" within a few blocks of our house.