The 1911 Weeks Act had allowed the purchase of land to enlarge the National Forest System. Two years after the Weeks Act was passed, over 700,000 acres (2,800 km²) had been purchased for the National Forest system in the Eastern United States. More than 2 million acres (8,000 km²) of land had been purchased by 1920.
The Clarke–McNary Act made it much easier for the Forest Service to buy land from willing sellers within predetermined national forest boundaries. It enabled the Secretary of Agriculture to work cooperatively with State officials for better forest protection, chiefly in fire control and water resources. It also provided for continuous production of timber. Additionally, the United States Department of Agriculture (USDA) began working with private forestland owners in reforestation. That was done by broadening the cooperative efforts to include producing and distributing tree seedlings and providing forestry assistance to farmers.
The laws also gave a strong impetus to states to establish and to support state forestry agencies. All 50 states now have a state forestry agency or forestry extension agency.
