attacks increased after the Sand Creek Massacre in Colorado in 1864, bringing more troops to the post, which was by now called Platte Bridge Station. In July 1865, Lt. Colonel William Collins' beloved son Lieutenant Caspar W. Collins was killed near the post by a group of Indian warriors, and three months later the garrison was renamed Fort Caspar in his son's honor.

In 1867, the troops were ordered to abandon Fort Caspar in favor of Fort Fetterman,