for railroad ROW reserch…preferably online can anyone help
Start at http://nationalmap.gov/historical/
Have you tried the ones at http://historicaerials.com ?
(Now if only the people looking at the quads understood what they were.)
The old northing and easting trick? Dang autocorrect…
The topo maps on maps.acme.com frequently are old enough to go back a couple of generations, merger-wise. And, you can change between topo and satellite, which can sometimes help sort out modern-day changes to the landscape.
You don’t say which ones and what size or plot you’re looking for. Hunting and fishing sporting goods stores may have a source, antique shops and flea markets, histoircal societyies, US Geodetic survey, even modern map makers like DeLoreme of Freeport, ME may have some or lead you to some. Look at the ads in Trains, too.
Not sure what area you’re looking for, but the University of New Hampshire Library has a great online set of historical USGS topos, but only for New England and New York.
http://docs.unh.edu/nhtopos/nhtopos.htm
So if you’re looking for anything beyond that, I guess this won’t help much… 
They’re obviously not on-line, but local libraries, and especially college libraries often have a plethora of such maps available for viewing in the library. Printing off whatever you can find on-line, then annotating that with what you see in the library may be beneficial.
And sometimes such resources have old “political” maps that can shed light on old railroads. The placement may or may not be exactly correct, but may give an idea of where you should look.