Fort Union National Monument is home to what was once the largest military post west of the Mississippi River, but only adobe and stone ruins remain today on the New Mexico prairie. These surviving walls are actually part of the third Fort Union in this area, and come September 20 you can join rangers for a special chance to visit the site of the first Fort and Arsenal, which is located just outside the park itself.

Why was there even one fort in what today seems to be a rather unlikely location?

With the acquisition of New Mexico in 1848, the United States assumed the role of protecting traders and travelers on the Santa Fe Trail and in the Southwest.  It was a daunting task, so to that end eleven outposts scattered throughout the Territory of New Mexico were consolidated at a strategic location near the junction of the Mountain and Cimarron branches of the Santa Fe Trail.

That post became the first Fort Union, but it was poorly built, and at the outbreak of the Civil War in 1861, a more substantial fort was deemed necessary. The second Fort Union was a massive earthen "fieldwork," later called the Star Fort; located about a mile east of the first fort, it was designed to block the Santa Fe Trail against fears of a Confederate advance through New Mexico from the south.

In March 1862, Union forces achieved a decisive victory at Glorieta Pass, ending the Confederate threat against Fort Union. Due to the construction techniques and materials used, the Star Fort was decidedly inhospitable for its inhabitants, so a more suitable fort was constructed not far from the earthworks.

If you visit Fort Union today, you'll see ruins of this third post, a "sprawling installation [that] contained three parts: the Post, the Quartermaster Depot, and the Ordinance Depot. It took several hundred civilians five years, from 1863 to 1868, to complete construction. The new buildings at Fort Union were constructed of adobe brick, the walls standing on stone foundations and coated with plaster." 

The location of the first Fort Union is separate from the main park unit, and is not normally open to the public. On Saturday, September 20, 2014, ranger-guided First Fort and Arsenal Tours will offer a once-a-year chance to visit the site of the original fort and see the remnants of Fort Union's arsenal, which was crucial in keeping the army of the Southwest supplied with arms and munitions.

A special focus of the tours will be the Fort Union's impact on the Red River War of 1874, along with other events during the Indian Wars period. The programs will be conducted at 9 a.m., 10:30 a.m., 12:15 p.m., and 2 p.m. Tour participants should meet at the visitor center 15 minutes prior to each program time, and then caravan out to the First Fort site. This program is being offered in partnership with the Fort Union Ranch.

Visitors attending these programs should wear sturdy walking shoes and a hat, and should bring sunblock, snacks and drinking water.

If you plan to visit this area, be sure you keep your "Fort Unions" straight. That was a rather popular name in an earlier era, and Fort Union Trading Post National Historic Site is located on the Montana-North Dakota border. It preserves what is described as "the most important fur trade post on the Upper Missouri River"... and is about a 970-mile drive north of its New Mexico counterpart. 

Fort Union National Monument is located in northern New Mexico, and can be reached by taking exit 366 from I-25 at Watrous, then driving eight miles on NM 161. The park is about 94 miles northeast of Santa Fe and 95 miles southwest of Raton, New Mexico. You'll find additional information to help plan a visit on the park website.