Fort Union was established in 1851 as the guardian of the Santa Fe Trail. During its forty-year history, three different forts were constructed close together. The third Fort Union was the largest in the American Southwest, and functioned as a military garrison, territorial arsenal, and military supply depot for the southwest. The largest visible network of Santa Fe Trail ruts can be seen here.
During the summer, scheduled interpretive talks, guided tours, and living history programs are offered. Commercial and school groups numbering ten or more, interested in a formal guided tour, may make advance reservations. A 1.6 mile, self-guided interpretive trail enables visitors to tour the ruins. Visitors may opt to do a shorter .5 mile self guided tour. Allow approximately two hours for visit.