It extends from the Mount Jefferson area east of Salem to the Calapooya Ridge which divides the watersheds of the Willamette and Umpqua rivers.

Those management goals included: "…securing favorable conditions of water flows, and to furnish a continuous supply of timber for the use and necessities of the citizens of the United States", protection of the forests from destruction by fire and depredations, and development of mineral resources, among other provisions.

Addie Morris and Cy Bingham were noteworthy early rangers in areas that would become the Willamette National Forest.

During the Great Depression and World War II, the Willamette National Forest became a representative of the federal government in the communities of the western Cascades.

Efforts were made to improve employment and economic conditions through the Civilian Conservation Corps and through the use of sustained yield forestry.

In 1962, the Columbus Day Storm downed an estimated 140 million board feet (330,000 m3) of timber and created many log jams on the rivers.

The Willamette's timber sales continued at about 750 million board feet (1,800,000 m3) per year through the 1970s; however, the price bid per thousand increased dramatically.

The "section 318" bill passed by the U.S. Congress increased the volume sold on the Willamette in 1990 to nearly 1 billion board feet (2,400,000 m3) of timber.

The forest receives 80 to 150 inches (2,000 to 3,800 millimeters)[9] of precipitation each year from moist onshore Pacific Ocean flow which encounters adiabatic cooling rising over the Cascades.

[9] The rain and snow melt drain into the McKenzie, Santiam, and Willamette rivers, which flow from the forest and provide high-quality drinking water to Eugene, Salem, Corvallis, and Albany.

The forest is home to over 300 species of fish and wildlife, including the northern spotted owl, mule deer, bald eagle, Chinook salmon, black-tailed deer, bull trout, black bear, cougar, southern red-backed vole, elk, wolverine, and several other sensitive and threatened species.

The forest is central to the famous controversy between the logging industry and the endangered species status of the northern spotted owl.

Environmentalists maintain that the forest was aggressively clearcut for many years threatening a federally listed endangered species.