When Congress failed to appropriate money for the park's protection in 1886, General Philip Sheridan sent the U.S. Cavalry to Yellowstone to maintain order in the park. This story of the parks' first protectors appears in Ken Burns's newest film, THE NATIONAL PARKS: AMERICA'S BEST IDEA, premiering Sunday-Friday, September 27 at 8 p.m. on DPTV. For more information on the film, visit