What discoveries and developments prompted the establishment of national parks?

In the early years of the nation, wilderness and nature were not seen as something to appreciate or protect, but as something to overcome. People believed that humans needed to master the elements and their environment in order to improve their livelihood and safety.

However, this view started changing in the 19th century. With the Industrial Revolution, people began to see the problems of cities and to appreciate the beauty and simplicity of a "natural life." The Romantic movement, as well as the Transcendentalist movement played an important role in this. Authors such as Henry David Thoreau discussed the benefits of nature, and people began to think of such natural regions as worthy of being protected.

The artist George Catlin was one of the first ones to suggest protecting the environment and culture of the Great Plains of the United States. He was concerned that westward expansion would destroy much of the beauty of the region. The first region to be protected in this way, however, was Yosemite Valley in 1864. However, the movement to protect nature became more significant following the Washburn expedition, which made important discoveries in the Yellowstone Country. Afterwards, other natural areas were protected by different entities, such as Montana and Lake Huron. National parks became more common during the 20th century.

the main reason that the constitution did not proclaim all men to be free and equal is because of the issue of slavery.