The Reconstruction treaties between Indian tribes and the US government allowed for the construction of railroads across Indian territory.
During Reconstruction, the 12 years after the Civil War, the United States began to reunite and grow into a more industrialized nation. This includes the desire for a transcontinental railroad. Thanks to laws passed during the Civil War, such as the Pacific Railway Act of 1862, the United States government was well on its way to establish an intricate network of connected railroads that would bring the United States together. However, the problem was that the United States designated some of the land they possessed to Native American tribes.
To ensure that their dream of an industrialized nation with a railroad came true, the government made deals with Indians by compensating them for the land being used for these railroads.