"Over the Fremont Highway from its junction with The Dalles-California Highway, US97, approximately two miles south of LaPine, southeasterly via Silver Lake, Summer Lake, and Paisley to its junction with the Lakeview-Burns Highway, US395, at Valley Falls."
~ ODOT, Descriptions of US and Oregon Routes, March 2007
OR-31 was created at the beginning of the Oregon state route system in 1932, running between US-97 in La Pine and OR-11 in Valley Falls and providing a connection between Central Oregon and Northeastern California and Northern Nevada east of the Sierra Nevadas. The only major change along this route is the highway it terminates at in the south; in 1935, OR-11 became US-395 with its extension into Oregon. Other than that, it's been the same highway for the past 75 years.