US 56: Kansas-Oklahoma-New Mexico

The Great Plains--US 56 heading pretty much straight-arrow to the southwest through southwest Kansas, the Oklahoma 'panhandle', and northeastern New Mexico.  Came within a few miles of the southeast corner of Colorado and right after crossing from Oklahoma into New Mexico (the shortest state-to-state land border in the US, BTW) we were close enough to the northwest corner of Texas to spit into it!