Johnson Creek originates in Boring, Oregon, and travels 26 miles west through Clackamas and Multnomah counties, and the cities of Gresham and Portland before reaching its confluence with the Willamette River in Milwaukie. The watershed covers 52 square miles.

Johnson Creek passes through upland forests, farms, residential communities, wildlife refuges, industrial properties, along trails and through golf courses. It is a natural refuge in an urban environment and one of Portland's most important resources.