The United States Forest Service is an agency of the United States Department of Agriculture

United States Department of Agriculture

The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

 that administers the nation's 155 national forests

United States National Forest

National Forest is a classification of federal lands in the United States.National Forests are largely forest and woodland areas owned by the federal government and managed by the United States Forest Service, part of the United States Department of Agriculture. Land management of these areas...

 and 20 national grasslands

United States National Grassland

National Grasslands are authorized by Title III of the Bankhead-Jones Farm Tenant Act. For administrative purposes, they are essentially identical to U.S. National Forests, except that grasslands are areas primarily consisting of prairie. Like National Forests, National Grasslands may be open for...

, which encompass 193 million acres (781,044 km²). Major divisions of the agency include the National Forest System, State and Private Forestry, and the Research and Development branch.
In 1876, Congress created the office of Special Agent in the Department of Agriculture to assess the quality and conditions of forests in the United States.