John Day came to Oregon in 1812 as part of an overland expedition to the new Pacific Fur Company post in Astoria. The once large party split up into many small groups before reaching Oregon Territory. While camped where the mouth of the Mah-hah River meets the Columbia, John Day and Ramsay Crooks were robbed of all their belongings, including clothing. They were rescued by a party of trappers also headed to Astoria. John Day became well known at the trading post, and whenever others passed the spot of the incident, they pointed out where he had been robbed. In this way, the Mah-hah River became known as the John Day River. John Day never came to this area; Thomas Condon named it the John Day Fossil Beds because of the river's role as a landmark and its importance in eroding and exposing fossil-bearing rock layers.