The Progressive Era saw a key debate between conservationists and preservationists. Conservationists like Pinchot argued for the sustainable management of resources—forests, water, minerals—so they could be used by future generations. Preservationists like Muir, on the other hand, wanted to protect the wilderness from all human interference. This philosophical divide influenced policies on land use and resource management.

This landmark law, signed by Roosevelt, allowed the president to designate national monuments, protecting landmarks, structures, and objects of historic or scientific interest on federal lands. It was a flexible and powerful tool to protect natural and cultural sites without the need for congressional approval. The act was used to establish places like the Grand Canyon as a national monument before it became a national park.

The Progressive Era was a crucial time for the expansion of the national park and forest systems. Yellowstone (1872) was the first national park, but it was under Roosevelt that the system grew significantly. Millions of acres were set aside for national forests and parks to protect them from logging, mining, and other industrial activities, ensuring that these lands would be preserved for future generations.

The Progressives were highly successful in raising public awareness about conservation and enacting lasting reforms. The creation of the U.S. Forest Service, the establishment of numerous national parks and forests, and the passing of key legislation like the Antiquities Act were transformative. These efforts protected millions of acres of land and laid the groundwork for modern environmental policy.