The mountain route was the rugged, northern route of the Santa Fe Trail. On the route, the brothers Charles and William Bent and Céran Saint Vrain built an adobe structure near the Arkansas River in 1833. This structure came to be known as Bent’s Old Fort, sometimes described as Castle of the Plains. The adobe walls were fourteen feet high and the central courtyard was surrounded by lower and upper levels of rooms. Behind the fort, there was an adobe corral for animals. On top of the high walls, prickly pear cacti were planted to keep out invaders.
In the 1830’s and 1840’s, Bent’s Old Fort was on the boundary line between the United States and Mexico. It was six hundred miles from the nearest town in Missouri. William Bent managed the fort and traded with Indians, Mexicans, and trappers for furs, mules, buffalo robes, blankets, and horses. It was a place for people to stop and rest while traveling on different trails. In 1846, Susan Magoffin, wife of a Santa Fe Trail trader, recovered from an injury here. In her diary, she left detailed descriptions of Bent’s Fort. Army Engineer, Lt. James Abert, a government map maker, drew detailed maps of the fort.
Between these two fort visitors, Bent’s Fort could be reconstructed with great accuracy. William Bent abandoned this fort in 1849 and built Bent’s New Fort in 1853, forty miles downstream on the Arkansas River from his fi rst fort. In 1976, the National Park Service reconstructed Bent’s Old Fort on the original location. Now it is called Bent’s Old Fort National Historic Site.