It was originally routed from Ada to Patterson on a former eastern heading of the now-defunct State Route 69, which was rerouted to Mount Cory (this route is now part of State Route 235).
It was originally routed from Ada to Patterson on the former northernmost section of the now-defunct SR 69. At the time of SR 81's current designation, SR 69 was rerouted to Mount Cory (this route is now part of SR 235).