Fort Keogh is a former United States Army post located at the western edge of modern Miles City, in the U.S. state of Montana. It is situated on the south bank of the Yellowstone River, at the mouth of the Tongue River. The development of Fort Keogh as a military installation soon stimulated traders to supply the liquor and other service businesses that were the beginning of Miles City. Today the former military post is a United States Department of Agriculture livestock and range research station. It is listed on the National Register of Historic Places.