The town of Okanogan began as a trading post established near the mouth of Salmon Creek by Frank "Pard" Cummings in 1886 when the Chief Moses Indian reservation was thrown open to white settlement. Born in Maine, Cummings traveled west in an ox-driven covered wagon.

Originally named Alma for Alma Kahlow, daughter of a Prussian farmer living here. The town had the second post office here. The name changed to Okanogan, the Indian name for the river that flows through the valley in 1907.