When Fort Massachusetts was built in 1852, the San Luis Valley was technically part of New Mexico Territory, acquired by the United States through the Treaty of Guadalupe Hidalgo just four years earlier. The fort served multiple purposes: it maintained order in the valley, provided a headquarters for Indian Agents, and signaled to Mexico that the United States considered the territory firmly its own. Major George A.H. Blake of the First Dragoons commanded the post, which sat at an elevation of 8,000 feet against the towering backdrop of Mount Blanca. The valley around it was vast and largely empty, home to Ute hunting grounds and only a scattering of settlers.

The fort's primary mission was to protect white settlers and Ute Indians from one another, a mandate that proved difficult to carry out peacefully. Tensions escalated until Governor Meriwether authorized military action, mustering 500 volunteers into service on January 31, 1855. Colonel Thomas T. Fauntleroy, commanding forces dispatched by Colonel John Garland, ordered his troops to pursue Chief Blanca and his band across the San Luis Valley. The pursuit lasted several days, driving the Ute forces across the open valley floor until the majority were killed or scattered. The campaign underscored the fort's role as a projection of federal power into a contested landscape.

Military scouts had originally chosen the site because it sat along the route settlers used to enter the valley. But by the time construction was finished, those settlers had discovered easier trails, and the fort found itself guarding empty ground. In 1856, the Army began building a replacement six miles to the south. The new installation consisted of twenty-two one-story adobe buildings, a significant upgrade from Fort Massachusetts. Completed in 1858, it was named Fort Garland in honor of Colonel John Garland. Fort Massachusetts was promptly abandoned. Kit Carson would later command Fort Garland during the Civil War, cementing its place in Western history while its predecessor faded into memory.

Nothing remains of Fort Massachusetts above ground today. The site sits on private land, closed to the public, at the base of one of Colorado's most dramatic fourteeners. Mount Blanca rises to 14,345 feet directly behind where the fort once stood, its massive bulk visible from across the San Luis Valley. Fort Garland, the replacement post, fared better in the long run. It operated until 1883 and is now preserved as a museum. The story of Fort Massachusetts endures as a reminder that even in the era of Manifest Destiny, location was everything, and a six-mile miscalculation could render a military installation obsolete before its logs had time to weather.