Final answer:
The Yosemite Grant Act, signed in 1864, started the process of setting aside lands for conservation, which was followed by the Yellowstone National Park Protection Act in 1872.
Step-by-step explanation:
The passage of the legislation to protect Yosemite, known as the Yosemite Grant Act, was a significant event in the history of the United States' approach to conservation. In 1864, President Abraham Lincoln signed this act, which marked the inception of the idea of national parks—a pivotal step towards the conservation of natural landscapes. This action by the federal government was the first to earmark a specific area of land for preservation and public use, setting a precedent for future presidents to follow. The Yellowstone National Park Protection Act came next in 1872, further solidifying the federal government's commitment to setting aside lands for ecological preservation and public enjoyment.
However, not all such efforts were successful. As highlighted, the Hetch Hetchy Valley in Yosemite National Park became a site of conflict and eventual loss for preservationists when Congress voted to dam the valley. Yet the debates and efforts of the time did lead to the eventual creation of the National Park System Organic Act in 1916, which declared that national parks were to be maintained without impairment for the benefit of future generations.