In 1823, William's father decided his son should become a military officer--William agreed, though he was then only eleven years old. Over the next several years, William's father and mother arranged their son's education and physical training with the aim of a successful life in the Army. Young William excelled in his academic studies and in his riding skills. He enjoyed an active social life and made personal friends of others he met of his age, including Jefferson Davis, Joseph E. Johnston, and Henry Clay, Jr.
Red-headed William joined the West Point Class of 1827 earning a reputation as a fun-loving daredevil. He was also known by his classmates as a serious student, especially of engineering and scientific subjects. He excelled in military classes, including horsemanship and tactics.
Upon graduation from West Point on July 1, 1831, he was commissioned as a Second Lieutenant. But after serving in several commands, he found garrison duty boring, and on September 30, 1836, he resigned his commission to work as an assistant United States civil engineer. On July 7, 1838, he was attracted to the revised "Topographical Engineering Corps", and rejoined the Army as a First Lieutenant.
The job of topographical officers was to serve as surveyors, explorers, and map makers. In 1838, the Corps had thirty-six officers, selected as the best soldier-scientists in the Army.
In 1844, he was assigned to conduct a Canadian boundary survey. In 1846, The British Commissioners commended him for his surveying techniques and the skillful and physically demanding survey he completed during severe winter months on our northern international boundary.
With the United States/Canadian border settled, Lt. Emory and his commander, Colonel Abert, became interested in our southern border and the southwest. What value were there to the United States were the vast largely unexplored expanses of land, desert, mountains, and rivers of the southwest? What should be our southern border with Mexico? Was there a route to expand our railroads to California? Colonel Abert needed additional verifiable data to report to Congress--information he deemed his Corps should compile and assimilate for publication.
The Mexican War resulted in a military expedition--to be known as The Army of the West. The troops were to explore lands from Kansas through today's New Mexico, Arizona, and on to California. Colonel Abert decided some of his engineers to go along. He chose Lt. Emory as leader of the team--he believed Lt. Emory was best qualified by physical attributes, scholarship, attitude, and devotion. The tasks he assigned Lt. Emory task was to explore the southwest and collect accurate records as an officer in the Army of the West's westward march of exploration.