Can anyone tell me the steepest mainline 
        gradients on US transcontinental lines?
         
        I think you'll find them moderately 
        steep - came through the Rockies in 1997 on the California Zephyr and 
        would be surprised if they weren't around 1 in 40 in places.  The 
        Americans have latterly used pretty powerful locos, particularly in the 
        mountainous country.  The Cajun Pass, on UP's line in California is 
        1 in 36.  Suggest you try a posting to misc.transport.rail.americas 
        or alt.railroad, you'll most likely get replies as a percent grade from 
        the locals.
         
        regards
         
        David Bennetts
        Canberra