U.S. 32 was a former designation for what is now US 6 between Chicago, IL and Council Bluffs, IA.
U.S. 33 currently links Dunlap, IN to Richmond, VA; it originally extended to St. Joseph, MI and passed through South Bend, IN.
U.S. 34 goes from Berwyn, IL (west of Chicago) to Granby, CO.
U.S. 35 currently runs from Michigan City, IN to St. Albans, WV, near Charleston. A new four-lane highway will extend the route to Hurricane, WV.
U.S. 36 links Uhrichsville, OH to Rocky Mountain National Park, CO. It has multiplexes with Interstate 72 (from Decatur, IL to Hannibal, MO) and Interstate 70 (from Byers to Denver, CO).
U.S. 37 was proposed for a route from Sellersburg, IN to Chattanooga, TN, via Nashville, TN. The route was never signed; if it were, the split routes for US 31 would've been eliminated (US 37 was to follow what is now US 31E).
U.S. 38 ran from Omaha, NE to Denver, CO. This routing has been replaced by US 6.
U.S. 39 has never been used in any known proposal.
U.S. 40 links Atlantic City, NJ to Park City, UT. Originally, it went as far as San Francisco, before Interstate 80 replaced it. US 40 split into US 40N and US 40S in Kansas and Colorado until the mid-1930s. For most of its route, it is parallelled by Interstate 70.
