1842. He was appointed a brevet second lieutenant in the 7th U.S. Infantry Regiment on July 1, 1842, and began his army service in the Southern United States. After graduation, in December 1843 he married Caroline Godbold, daughter of a prominent Alabama planter family. They had two children together: son Earl Van Dorn, Jr. (b. 1855) and daughter Olivia (1852-1878). Van Dorn and the 7th were on garrison duty at Fort Pike, Louisiana, in 1842–43, and were stationed at Fort Morgan, Alabama, briefly in 1843. He did garrison duty at the Mount Vernon Arsenal in Alabama from 1843 into 1844. He was ordered to Pensacola harbor in Florida from 1844 to 1845, during which Van Dorn was promoted to second lieutenant on November 30, 1844. War with Mexico Van Dorn was part of the 7th U.S. Infantry when Texas was occupied by the U.S. Army from 1845 into 1846. During the early stages of the Mexican–American War, he was garrisoned at Fort Texas (Fort Brown) in Brownsville, defending the border from the southernmost town in Texas. Van Dorn saw action at the Battle of Monterrey on September 21–23, 1846, and during the Siege of Vera Cruz from March 9–29, 1847. He was transferred to Gen. Winfield Scott's command in early 1847 and promoted to first lieutenant on March 3. Van Dorn fought well in the rest of his engagements in Mexico, earning himself two brevet promotions for performance; he was appointed a brevet captain on April 18 for his participation at the Battle of Cerro Gordo, and to major on August 20 for his actions near Mexico City, including the Battle of Contreras, the Battle of Churubusco, and at the Belén Gate. Van Dorn was wounded in the foot near Mexico City on September 3, and wounded again during the storming of Belén Gate on September 13. After the war with Mexico, Van Dorn served as aide-de-camp to Brev. Maj. Gen Persifor F. Smith from April 3, 1847, to May 20, 1848. He and the 7th were in garrison at Baton Rouge, Louisiana, from 1848 into 1849. Later in 1849 they served at Jefferson Barracks in Lemay, Missouri, south of St. Louis. He saw action in Florida against the Seminole from 1849 to 1850, as the United States tried to dislodge them from the region. Some Seminole succeeded in evading those efforts and survived in the Everglades; they were the