The Columbia River Gorge National Scenic Area is a 292,500-acre protected area that is managed by the US Forest Service. The scenic area runs from the mouths of the Sandy River to the Deschutes River and includes land in both southern Washington and northern Oregon. This area has an extremely high density of waterfalls, including Multnomah Falls, the highest waterfall in Oregon, and is a very popular recreation area and tourist destination.
US Forest Service website: http://www.fs.usda.gov/crgnsa