|According to Oregon Geographic Names, 6th Edition by Lewis L.
The Clarno postoffice was named for one of the earliest white settlers on the John Day River, Andrew Clarno. The postoffice was generally situated near the John Day Bridge and, depending on who could be prevailed upon to take care of it, was in Wasco County, Wheeler County, and even Gilliam County.Clarno has an elevation of 1304 feet.The postoffice was established Sept. 15, 1894, with Nannie Chichester postmaster. When Andrew Clarno settled on the John Day River, he had no neighbors. Stockmen in those days did not feel the need of any. When he heard that a friend had settled on a homestead 20 miles away, near the present site of Fossil, he rode over on horseback and said: "Bill, don't you think you're crowding me a little?" Maps and postal records show a postoffice named Crown Rock in the present locality of Clarno. It had been named for a prominent rock formation nearby.