The Saddle Mountains area is just North of Mattawa, WA. It is about 5700 acres of public lands, consisting of mountains covered with small amounts of underbrush and criss-crossed with service roads, mainly along the power lines and leading to communication stations.
This is a good area for a relaxing ride in wide open country. Most of the riding consists of easy gravel roads, but at the Western edge you can find a sandy play area, and some very steep hill climbs. There are a couple of canyons to crawl through, which is the most interesting part.
Get details including directions, staging areas, maps, and difficulty levels in the UTV Guide to WA State.