The Department of the West was a military administrative division of the United States Army established in 1866. It was created to manage military operations and oversee the administration of territories in the western United States following the Civil War. The department played a crucial role in maintaining order and supporting westward expansion. Headquartered in San Francisco, California, the Department of the West encompassed various states and territories, including California, Nevada, and parts of Arizona. It was responsible for coordinating military efforts against Native American tribes and ensuring the safety of settlers and infrastructure in the region. The department was eventually dissolved in 1886.