Seneca is a city in Grant County, Oregon, United States. It is located in the Blue Mountains about 23 miles south of Canyon City, on U.S. Route 395, on the edge of the Malheur National Forest. As of t

The Silvies River flows for about 119 miles through Grant and Harney counties in the U.S. state of Oregon. The river drains 1,273 square miles of the northern Harney Basin.