Built of Earth: How Bent's Old Fort Was Made, and When

Bent's Fort, the great adobe trading post on the Arkansas River, looked like a castle on the plains: thick earthen walls, towers at two corners, portholes along the battlements, nearly fireproof and easy to defend. It was built of the ground it stood on, by workers from Taos, and modeled on the fortified towns of northern New Mexico. How long it took, and exactly when, are still open questions.

Elevations of the fort drawn for the National Park Service's 1976 reconstruction. Credit: National Park Service.

Building in adobe

Charles Bent is thought to have designed the fort, with his brother William in charge of construction, drawing perhaps on forts he had seen in the East and on the pueblos of Mexican territory. For how it was built, historians depend mostly on William's son George Bent. Writing in 1905, George said Charles hired about 100 New Mexicans from Taos to make the adobes:

• Mud and straw were mixed with feet, shovels and hoes in a shallow pit on site, then packed by hand into wooden molds.
• One resident in 1846 gave the bricks' size as 18 by 9 by 4 inches.
• Accounts of the mix differ. George Bird Grinnell, probably relying on George Bent, said Charles added wagonloads of Mexican wool to lengthen the adobes' life; Frank Delisle, a former employee who claimed to have supervised construction, said clay and chopped straw; the visitor Matthew C. Field wrote of "simple prairie soil" held together with straw and grass.
• Adobe and roof timbers probably came mostly from nearby; Kit Carson told George Bent he had been hired to lead 12 men cutting timber for the fort. Window glass came carefully over the Santa Fe Trail, and the fort's blacksmith and carpenter could make hardware and woodwork on site.

A New Mexican design

The fort closely resembled the plazas (fortified towns) and haciendas (ranch compounds) of northern New Mexico: rooms around a central courtyard, their back walls forming one windowless outer wall, a double gate through an entrance hall (zaguán) as the only way in, a corral at the rear, and defensive towers (torreones) — sometimes two, at opposite corners, as at Bent's Fort. George Bent described its rooms as "built against the walls in the Mexican fashion." It also echoes the adobe presidios of New Spain's northern frontier. Like them, it was built for defense; a visitor in 1845 called it "a place of security."

When was it built?

The record is full of gaps and contradictions:

• Smallpox. George Bent said an outbreak halted construction: "My father, Wm. Bent, & [Ceran] St. Vrain were among the first to take the small Pox.... every body left except those that had the small pox." The Bents told the Cheyennes and Arapahos to stay away until it passed. Smallpox had broken out among the Shawnees along the Santa Fe Trail in summer 1831 and reached the Delawares, frequent travelers to the Upper Arkansas, by October — possibly the same epidemic, and a clue to the date.
• How long? Several sources say four years. The Park Service's 1976 reconstruction took about 14 months with trucks, power tools and an adobe-making machine — but it copied the larger fort of 1846. Adobes can only be made and laid in warm, dry weather, and need about a week of it to cure, so less than a year seems unlikely; but experienced New Mexican builders would hardly have needed four.
• Historians disagree. David Lavender concluded it was begun in 1833 and finished in 1834; LeRoy Hafen pointed to 1833; Janet Lecompte said not before 1834; archaeologist Douglas C. Comer, from pottery in the fort's dumps, suggests about 1831. The Park Service's own account gives construction starting in 1833 and probably ending in spring 1835.

The one certainty is that the fort was open by August 6, 1835, when Col. Henry Dodge's expedition of U.S. dragoons arrived. Four members of the expedition mentioned it in their journals, and Capt. Lemuel Ford drew a small map showing the fort.

Sources

Based on "Architecture Born of Earth and Colonization," National Park Service (Bent's Old Fort National Historic Site), adapted from Mark L. Gardner's 2004 Historic Resource Study, Bent's Old Fort on the Arkansas; a work of the United States government in the public domain.