Two references on railroad archaeology that come to mind immediately
are: Rossillon, Mary P., 1984, The Curencanti Archaeological Project:
The Archaeology of Marion, an Historic Railroad Camp in Curecanti
National Recreation Area, Colorado.  Midwest Archeological Center,
Occassional Studies in Anthropology No.9, Lincoln, Nebraska; and
Harcourt, James P., 1992, The Ties That Bind, An Archaeologist Looks
At The Railroad, FIELDNOTES Newsletter of the Arkansas Archeological
Society 246:5-9 (May/June).