Hi,
Having worked as a civil engineer during collage, the county plats are an excellent source of info.
On one plat here in DeKalb Co GA, I found a partial yard track plan for the Roswell RR and Southern Rwy in Chamblee.
The counties try to keep as much on properties as possible. I worked on one job that the legal description said that one boundry was the 1804 Indian Treaty Line. The property had been in the same family from 1804+- to 1975.
When properties are bought or sold, frequently a title search is done that includes following the property back as far as possible to make sure no forgotten liens are in force.
Hope this additional info is useful.
Doug