On September 19, 1939, Secretary of Agriculture Henry Wallace issued a series of "U-Regulations" (U-1, U-2, and U-2A) to cover the administration of certain areas within the national forests. Written by the renowned wilderness advocate Bob Marshall, who worked for the Forest Service at the time, the U-Regulations superseded the L-20 Regulation and provided for the designation of Wilderness Areas and Wild Areas within national forests, instead of the former classification as Primitive Areas.

Under the new regulations, Wilderness Areas (U-1 areas) were to contain contiguous blocks of at least 100,000 acres in which there would be no roads or motorized transportation, no commercial timber harvest, and no special use permits for hotels, lodges, resorts, or similar facilities. Most other rights of public access were open, including prospecting and developing mineral resources. U-1 areas could only be modified or eliminated by order of the Secretary of Agriculture.

The Wild Areas, or U-2 areas, were similar to Wilderness Areas but in smaller 5,000 to 100,000-acre units. Authority for these areas rested with the Chief of the Forest Service, pending a public review process.

Regulation U-2A established that existing Primitive Areas would be administered in the same fashion as new Wilderness Areas.

The U-Regulations governed Forest Service wilderness policy for more than twenty years until the passage of the Wilderness Act in 1964. In 1963, the agency managed 14.5 million acres of Primitive, Wilderness, Wild, and Canoe Areas in 86 units across the country.

Source:

"Briefing on Primitive Areas in the National Forest System," Statement of M. Rupert Cutler, Assistant Secretary for Conservation, Research, and Education, U. S. Department of Agriculture, Before Subcommittee on Public Lands of the Committee on Interior and Insular Affairs, U.S. House of Representatives, July 24, 1979.

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