John Day

The John Day River is a tributary of the Columbia River, approximately 284 miles (457 km) long, in northeastern Oregon in the United States. It is known as the Mah-Hah River by the Cayuse people. Undammed along its entire length, the river is the fourth longest free-flowing river in the contiguous United States. There is extensive use of its waters for irrigation. Its course furnishes habitat for diverse species, including wild steelhead and Chinook salmon runs. However, the steelhead populations are under federal Endangered Species Act (ESA) protections, and the Chinook salmon have been proposed for such protection.

The river was named for John Day, a member of the Pacific Fur Company's overland expedition to the mouth of the Columbia River that left Missouri in 1810. Day struggled through eastern Oregon during the winter of 1811–12. While descending the Columbia River in April 1812, he and Ramsay Crooks were robbed and stripped naked by Native Americans at the mouth of the river that now bears his name, forcing them to hike 80 miles (130 km) back to friendly Umatilla Indians under extreme conditions.