Map of US highway 56 and family, and US 412
US 56 is represented by the purple line from Kansas City to Springer NM.
US 156 (historic) is the red line from Ellsworth to Garden City KS.
US 412 is also shown on this map (the green line from Columbia TN to Springer NM). 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 56 family, if it were to be assigned a number US x56. (This is just one of several other possibilities that make more sense than 412; I've also included the route on the maps for US 60, US 62, US 64, and US 70).