Wow! The Oklahoma Department of Transportation has scanned and posted official Oklahoma state highway maps going back to statehood. There are the annual maps produced from 1924 to 1996, the biennial maps produced since 1997, and a few early maps from 1873, 1907, 1916, 1919, and 1921. For most of the maps, there's also a scan and a description of the back of the map.

I've been looking at the 1916 map, which shows the highways overlaid on the township and section grid, along with railways, rivers, and county lines. Although many of the inter-town routes on the map were later incorporated into numbered highways, not all were. For example, there's the road from Tulsa to Jenks: Peoria to 71st to Lewis to the 96th Street bridge. Or from Catoosa to Broken Arrow: 193rd to 11th to Lynn Lane. The road from Tulsa to Bixby and Broken Arrow went down Harvard and 51st to Memorial, with the BA route splitting off at 71st and the Bixby route, shifting 1 mile east at 111th to Mingo. The map shows the bridge crossing about halfway between Mingo and Memorial.