Rich in prehistoric, pueblo-type culture, and noted by the explorer Jedediah Smith in 1826, Moapa Valley is crossed by the old Spanish Trail.

In 1865 Brigham Young sent 75 families to settle the area, to grow cotton for the people of Utah, and to connect Utah with the Pacific Ocean via the Colorado River.

Located near the junction of the Muddy and Virgin Rivers, and now under Lake Mead, the "Cotton Mission" was named St. Thomas for its leader, Thomas Smith. A prosperous, self-contained agriculture was built up in the valley, which included orchards, vineyards, cotton, grains and vegetables.

The December, 1870 survey placed the valley in Nevada and because Nevada taxes were greater than those of Utah, the settlers, now including those in St. Joseph, (Old) Overton, West Point and Logandale, began leaving two months later. They left the results of seven years of labor, more than 18 miles of irrigation canal and several hundred acres of cleared land.

Other Mormons resettled the land in 1880. The area remains one of the most agriculturally productive in the state.