OK, just an excuse to post this The C&O Canal Bicycling Guide - Welcome! The C&O canal operated into the 1920s, before the railroads finally killed it. It is now a 184 mile long bike/hike path that is part of a larger Park. Like many old railroad ROW, it was converted rather than left to rot. It also means a maintained route that is not on the road system. The post site cover the canal route and has many photos - worth the time to have a look IMO.
arizona Maps - azbikeped.org REI has an interactive map for all mt bike trails Western States (aka Tevis Trail) Mountain Bike Trail, Sunnyside-Tahoe City, California
My brother lives i Tucson - and is big on riding bicycles. Besides the Tour de Tucson, there is the Arizona Trail. Mexico to Utah! Arizona Trail - Wikipedia