Fur traders named this stream for John Day, a pioneer trapper who died in the valley north of here on Feb. 16, 1820. John Day had started west with John Jacob Astor’s Pacific Fur Company, which discovered Snake River Valley to the south of here in 1811. After 1816 he joined Donald Mackensie’s band of fur hunters, who finally spent the winter of 1819-1820 in what is now known as Little Lost River Valley. For many years, trappers and mapmakers referred to Mackensie’s campground as on John Day’s River, which is now Little Lost River.