"Over the Dairy-Bonanza Highway from its junction with the Klamath Falls-Lakeview Highway, OR140, at Dairy, easterly to Bonanza."
~ ODOT, Descriptions of US and Oregon Routes, March 2007
OR-70 was created at the inception of the Oregon route numbering system in 1932, heading between OR-66 in Dairy to the town of Bonanza. The only change associated with OR-70 between then and now is the route designation of the highway on its western terminus, which became OR-140 in 1966. The road that OR-70 travels on continues as a county road (Market St. into Bly Mountain Cutoff Rd., or Klamath County Road #1063 according to Mike Wiley) north of Bonanza, with an "End State Highway Maintenance" sign being the only indication of OR-70's termination. I'm not sure if this road deserves primary state highway and route status...it's one of the shortest routes in Oregon's highway system.