Pair of antique mid 19th century lithograph on paper of snakes book plates. Published by the US Pacific Railroad Exploration and Surveys 47th parallel. Unframed, age toning. The U.S. Pacific Railroad Surveys (USPRR) were a massive 1853–1855 congressional initiative by the U.S. Army Corps of Topographical Engineers to determine the best route for a transcontinental railroad. The surveys spanned multiple latitudes.