Another great resource is the USGS. They have a site that you can explore their historical topographical maps and download them. Many of these, dating back to the turn of the 20th century, have railroads marked out - even with the owner.
https://ngmdb.usgs.gov/topovie...wer/#4/39.98/-100.06
ArcGIS also has a website with a similar feature:
https://livingatlas.arcgis.com...oexplorer/index.html