Soda Mountain is located in downtown Sumpter. Yes, Sumpter, a city of about 200 people in the Elkhorn Range of the Blue Mountains of northeastern Oregon. Soda Mountain started as a tent of supplies at July and Labor Day Flea Markets in 2001. It got walls March 18, 2011. You and your animal companion(s) are welcome to visit us any time we’re open, which is almost every weekend of the year.