Major Stephen H. Long’s 1820 expedition to the Rocky Mountains began on the banks of the Missouri River north of present-day Omaha, Nebraska on June 6, and followed a westerly path along the Loup and Platte Rivers across most of present-day Nebraska and the along the South Platte to the Front Range of Colorado.
The expedition worked its way south along the Front Range to the Arkansas River and then down the Arkansas River to the present day location of Rocky Ford. At Rocky Ford, the party divided into two groups and the main part of the expedition went south in search of the Red River. Confusing the Canadian River for the Red, they followed the Canadian River across eastern New Mexico, the Panhandle of Texas and across Oklahoma.
The scientific personnel were Edwin James (botanist, geologist and surgeon), Thomas Say (zoologist), Titian Peale (naturalist and artist), as well as the official artist of the expedition, Samuel Seymour.
Edwin James returned from the expedition with about 700 species of plants. About 140 of these were new species and were subsequently described by either James himself or by other botanists. Notable plants collected by James that were new to science are the Colorado blue columbine (Aquilegia coerulea), narrowleaf cottonwood (Populus angustifolia), Sand sage (Artimisia filifolia), and mesquite (Prosopis glandulosa).
The expedition also described 10 new species of mammals, as well as 10 new species of birds.