Final answer:
The Bozeman Trail was closed in 1868 by a treaty with the Sioux Nation, according to the Second Treaty of Fort Laramie. Conflicts such as Red Cloud's War and the discovery of gold in the Black Hills led to increased tensions and the eventual breaking of this treaty.
Step-by-step explanation:
The Bozeman Trail was closed in 1868 by a treaty with the Sioux Nation. This treaty was known as the Second Treaty of Fort Laramie, which acknowledged Sioux ownership of the Black Hills, and this agreement effectively led to the closure of the trail. The Sioux, along with their allies, had engaged in a series of conflicts known as Red Cloud's War to resist the encroachments of settlers and to protect their lands. The treaty was an outcome of these conflicts, promising the Sioux territory in parts of present-day Montana, Wyoming, North Dakota, and South Dakota.However, the discovery of gold in the Black Hillsled to widespread disregard for the treaty. Despite the formal closure of the Bozeman Trail following the treaty, the lure of gold and subsequent white settlement eventually led to renewed conflicts, resulting in events such as the infamous Battle of Little Bighorn. After the discovery of gold, the U.S. government sought to claim these lands from the Sioux, leading to further disregard for the treaty agreements and increasing tensions between the U.S. government and Native American tribes.