Forest Park puts 5,100 acres of forest into the heart of urban Portland. In fact, the park is one of the nation’s largest urban forest reserves. The park is a buffer between industrial activity and residential neighborhoods. This buffer reduces some of the negative qualities associated with industry, such as noise and air pollution. The park offers significant open space with native plant species that generate an impressive amount of habitat within the city. The vegetation not only improves air quality for the city but also the quality of rainwater before it enters the Willamette River. Completed in 1948, the park is a second-growth forest running parallel to the river, along a steep hillside for nearly eight miles.

In 1903, the Municipal Park Commission brought in the famous landscape architecture firm, Olmsted Brothers, to prepare a park planning study for the city. They recommended acquiring the wooded hills west of the Willamette River for a park with a wild, woodland character. The establishment of the park itself, though, would take nearly another 45 years. The land for the park was largely deeded to the city in small parcels by civic-minded landowners and individuals who discovered the landslide-prone nature of their property and defaulted on their claims.

The Olmsted Brothers also recommended developing a 40-mile loop around the city. Wildwood Trail is the longest trail in the park. It's composed of 27 miles in Forest Park and three miles in Washington Park. This trail is the longest section of the 40 Mile Loop, a network that has now grown to 150 miles, reaching many parts of the Portland metropolitan area.