Simcoe Mountains

The Simcoe Mountains Volcanic Field, sometimes called the Simcoe Highlands, is a group of lava flows and extinct cinder cones located to the east of the Cascade Range in south-central Washington, United States. The mountains lie within Klickitat and Yakima Counties with the northern half making up part of the Yakama Indian Reservation. Although the volcanic field is located near the Cascade Arc of volcanoes, it is an intraplate volcanic field rather than having activity sourced from the Cascadia subduction zone. The last known eruption was about 631,000 years ago.

The Saddle Mountains was an important transportation corridor for Native Americans in the region, including the Yakama, with people passing over then to get between the Yakima Valley to the north and traditional fishing grounds along the Columbia River to the south. During the Yakima War, the United States Army constructed a road through the mountains to provide better access to forts on either side. Today it is traversed by U.S. Route 97 which passes over Satus Pass.

The upper slopes of the Simcoe Mountains are forested while the lower slopes are covered by grassland in a more arid climate. The area provides habitat for a variety of plant and animal life in different elevation-dependant ecological zones, both on land and in streams draining the area. Waterways flow into the Yakima and Klickitat Rivers which ultimately flow to the Columbia.