Map of US highway 50 and family, and US 400
US 50 is represented by the purple line beginning in Ocean City MD. Its western terminus is currently in Sacramento CA; the red line extending west of there to San Francisco is the historic extent of US 50. Its alternate route in Nevada is shown as a blue line, while historic routes through Nevada and Utah are shown in red. Through Kansas, US 50 now follows what was once designated US 50-S; historic US 50-N is shown in red.
US 150 is the blue line from Quad Cities IL to Mt. Vernon KY.
US 250 is the blue line from Sandusky OH to Richmond VA.
US 350 is the blue line from La Junta to Trinidad CO.
US 450 (historic) is the red line from Walsenburg CO to Crescent Jct. UT.
US 550 is the blue line from Montrose CO to Bernalillo NM; its historic route from Shiprock to Aztec NM is shown in red.
US 650 (historic) is the red line from Salida to Buena Vista CO.
US 400 is also shown on this map (the green line from near Joplin MO to Granada CO). Because its number is a major violation of US route numbering conventions, I included it on this map to demonstrate how the highway would fit into the US 50 family, if it were to be assigned a number US x50. (This is just one possibility that makes more sense than 400; I've also included the route on the maps for US 54 and US 66).