Final answer:
President Ulysses S. Grant signed the Yellowstone National Park Protection Act in 1872, which established Yellowstone National Park. This act was preceded by President Lincoln's Yosemite Grant Act in 1864. President Theodore Roosevelt later expanded the conservation of public lands, establishing many national parks, monuments, and forests.
Step-by-step explanation:
The individual responsible for setting aside tracks of land that have historic scientific or scenic significance as the first national parks was President Ulysses S. Grant.
In 1872, President Grant signed the Yellowstone National Park Protection Act which established Yellowstone as the first national park for the benefit of the American public.
However, it is important to note that President Abraham Lincoln laid the groundwork in 1864 with the Yosemite Grant Act, protecting Yosemite Valley and laying the precedent for national parks.
Following these actions, subsequent presidents, including Theodore Roosevelt, continued to preserve public lands for environmental protection and public enjoyment.
President Roosevelt significantly expanded these conservation efforts during his presidency in the early 20th century, establishing 18 national monuments, 51 federal bird preserves, five national parks, and over 150 national forests.
This amounted to about 230 million acres of public land reserved for ecological preservation and the benefit of future generations.