William Seaton Henry, United States Army officer, son of John V. Henry, a prominent New York lawyer, was born at Albany, New York, in May 1816. He was married at New Orleans in 1837 to Arietta Livingston. They had two daughters and one son, Guy Vernor Henry, who became a brigadier general in the United States Army.
Henry attended the United States Military Academy at West Point and upon graduation in June 1835 was assigned as a brevet second lieutenant to the Third Infantry regiment. He served continuously with the Third throughout his military career. In April 1836 his regiment marched from Fort Jesup, Louisiana, to the Sabine River, where it formed a part of the force of Gen. Edmund P. Gaines, who had been ordered to take post near that river during Antonio López de Santa Anna's movement through Texas. In the summer of 1838 Henry was detailed to proceed to Nacogdoches, Texas, to confer with Sam Houston on Indian disturbances. He continued to serve at various posts in Louisiana, Arkansas, Kansas, and Florida until July 1845, when he and his Company K of the Third Infantry were the first of Gen. Zachary Taylor's forces to disembark at Corpus Christi. He remained with the army of occupation during its stay at Corpus Christi, made the overland march to the Rio Grande, and fought in the Mexican War battles of Palo Alto and Resaca de la Palma. Shortly after those battles, Henry received his promotion to captain and, except for a brief interval due to illness, served continuously in Mexico throughout the war. During the war he wrote a series of descriptive letters that were published in the Spirit of the Times, a weekly newspaper published in New York, under the pseudonym G**DE L***. These letters, revised and published in 1847 as Campaign Sketches of the War with Mexico, contain one of the best detailed accounts of the advance of Taylor's army of occupation from the Nueces to the Rio Grande.
In the fall of 1848 Henry and six companies of the Third Infantry under the command of Bvt. Maj. Jefferson Van Horne were ordered from Pascagoula, Mississippi, to San Antonio, Texas, to await orders for further movement to El Paso. Henry described the trip to San Antonio, the stay in the camp on Salado Creek, and the subsequent overland trip to El Paso in a series of letters to the Spirit of the Times in 1849–50. His account was the first published description of what became known as the southern route to El Paso, a route that ran from San Antonio west to the site of present-day Del Rio, then north along the Devils River and the Pecos River, and then west through the Davis Mountains to the Rio Grande. The trek took 3½ months and was made by one of the largest assemblages to travel across Texas. The train consisted of more than 600 people, more than 300 wagons, and about 2,500 animals. Accompanying the train were several parties of civilians bound for California and the goldfields, one of which was led by Col. John C. (Jack) Hays.
After arriving at El Paso, Major Henry and his company were posted to San Elizario Presidio, twenty-five miles south of El Paso. He and his men made one extended trip into the Guadalupe Mountains in pursuit of Indians, and in 1850 served as escort to Maj. Robert S. Neighbors, Texas commissioner, to Santa Fe. As an act of courtesy, Henry supplied Neighbors with forage for his animals from the army quartermaster stores. For doing so he was court-martialed and received a reprimand and a fine. The Texas legislature subsequently passed a resolution praising Henry and authorizing the state treasurer to refund to him the ten-dollar fine that had been imposed by the army. After Henry's death, the legislature also granted a league of land to his widow and children. After the court-martial, Henry left El Paso, on August 26, 1850, for duty in New York City. He traveled over the northern route from El Paso to San Antonio, which he again described for the readers of the Spirit of the Times. This trip, which took only 17½ days, was hailed in the press as the "quickest trip ever made with wagons" from El Paso to San Antonio. Major Henry died in New York City on March 5, 1851, at the age of 34, and was buried at the Military Academy, West Point, New York.