The Native Americans felt so strongly about the land where Custer's Last Stand was fought because it had been there home for several years. They felt that it was unfair that the federal government would force them to move elsewhere just because gold was found on that land. To show their resistance, the Native Americans refused to move from their territory by the deadline given by the federal government.
When Custer and members of the US military went to confront these tribes (Lakota Sioux and Cheyenne) Custer severely underestimated how many troops there would be from these tribes. Lead by Sitting Bull, the Sioux and Cheyenne overwhelmed the American forces, resulting in an extremely embarrassing loss for the US military.