This illustration of Lieutenant Zebulon M. Pike is taken from an account of his military expedition from western Louisiana to the interior parts of New Spain conducted between 1806 and 1807. Zebulon Pike was an army lieutenant sent by the U.S. government to explore the southern part of the Louisiana Purchase in 1806. Upon his return, Pike prepared a report to the U.S. government in which he described the Plains as the "Great American Desert."