In the CW times, distances were usually measured post office to post office or railroad depot to depot, along any rail lines. If you can locate the rail depot as it was in the 1860s and the post office in that time period use a drawing compass to strike a circle around the two points with the distance set as the radii of the circles. If you're looking for a point actually ON the rail line at an "X" distance, then measure from the RR depot.
Make sure the roads are the PROPER roadways. For instance, in Jackson, Raymond Road running from South Terry Road, westerly is the original Jackson to Raymond Road; South Robinson Road is NOT. Clinton Boulevard running out of Jackson, to Clinton is the original Jackson to Clinton Road. Terry Road is the original Jackson to Terry Road (duh). It is also the original route of the US 51 Highway that runs north and south through Jackson. It was the only highway, running north and south before I-55 was built in 1966. For the original roads running east and west out of Jackson toward Vicksburg, FORGET I-20 and U.S. 80. There are very few places where U.S. 80 follows the original route. Too few to worry about and I-20 can be completely ignored. There were 2 routes running from Jackson to Vicksburg; one north and the other south of both I-20 AND U.S. 80.
If you live locally, go to the Mississippi State Archives, just off of State Street and join. Then make full use of the information there. They have copies of most old Mississippi newspapers, city and county maps, private diaries, etc. There's no membership fees for Mississippi residents, but there are costs for photocopies of material. They have the capability to photocopy the larger items such as maps, too. The charges for coping are reasonable, but call before you go there the first time, to find out how the payments can be made. It might save you a fair amount of time in your research on your first trip. It's become natural after the first trip.
