Prairies and Grasslands

Bent’s Old Fort National Historic Site features a reconstructed trading post located along the Arkansas River in the Lower Arkansas River Valley of southeastern Colorado. The river’s water supply and vegetation made this an ideal location for the Bent brothers to establish trade in the region their trading post.

The park belongs to the western section of the Great Plains, stretching from the Rocky Mountains to the Missouri River. More specifically, the fort’s surrounding shortgrass prairie landscape, an area characterized by annual rainfall between 15 and 25 inches, made the adjacent Arkansas River’s proximity crucial.

The broad flood plain cut a series of flat-topped hills, called benches, along the river’s flank. Because of the river’s course over time, elevation at Bent’s Old Fort gradually varies from 4035 feet to an average of 4300 feet north and south of the valley.

Plains cottonwoods and the peachleaf willow flourish along the Arkansas River, where they have access to the abundant water they require. The river bottom contains various mixed grasses, riparian, and wetland plant species. These riparian species which thrive in floodplains help to stabilize riverbanks.

Further out from the river grows the vegetation that ushered the buffalo robe trade to its economic peak. Blue grama and buffalo grasses, making up 80% of the shortgrass prairie enticed large herds of grazing buffalo. These grasses typically grow to about six inches tall and are preferred as buffalo forage to the grass species found among the tall grass prairie.

In addition to the blue grama and buffalo grass species are other drought-tolerant grasses, such as sand dropseed grass, Western wheatgrass, and side-oats grama, which reach one to three feet in height. Dominant shrub species include sandbar willow and sand sage. Sandbar willow grows along rivers and areas prone to flooding, forming thickets three to 20 feet high with narrow, serrated leaves. The aromatic, silvery-green, feathery leaves of the sand sage plume thrive in the sandy soil by the river’s edge. Because both native and non-native species compete for survival on park grounds, an ongoing park project is being conducted to remove non-native, crop, and exotic plants while restoring the native species.

The landscape of the 1830s trading post, the native homelands of the southern Cheyenne and Arapaho, eventually urged settlers to agricultural pursuits with its abundant grazable grasslands. Traces of those original plant species are still seen occurring naturally as they did years ago within the wide-open spaces surrounding Bent’s Old Fort.

Text written by Volunteer Ellen Martin, 2025.