GR Van from MyLandofMisery correctly guessed the location of the photos as old US 166 west of Sarcoxie, MO. 166 originally ran from Springfield, MO to South Haven, KS. However, in the early to mid 1960's, much of its Missouri alignment (from near Mt Vernon, heading west) was paralleled by Interstate 44, rendering 166 redundant.
If you look closely at the original photos, you can see where 166 was cut off by I-44. The 2 maps scans below show US 166 as it was in 1959 and in 1963. In 1963, I-44 was still under construction in many area, but had already cut-off part of 166.
A few years later, 166 would have its route shortened to just one mile in Missouri.
Much of what was once US 166 still exists and is driveable, but you can't always rely on a highway map to find it. Sometimes, it takes a little "detective work". I found this section almost by accident: I spotted it from I-44 and thought it might be old 166, but I didn't know for sure until I checked some old maps. Sometimes, though, you just have to hit the road and look for it.