At some point the toll road was turned over to the local governments, who I guess turned it over to the state for a highway. The road seems to use the current forest service road to Osier then follow the toll road route over Cumbres to Chama. From what I can find the "present" route up the Conejos River and over La Manga Pass dates from around 1923.
One has to wonder what kind of improvements were made to the road to make it a "highway". There has never been any signs of bridges where the road crossed Osier Creek, Cascade Creek, Long Creek and the Los Pinos River. Back then you had better be good at fording creeks and rivers.