Trevanion Theodore Teel, Confederate Army officer and lawyer, was born in Pittsburgh, Pennsylvania, on August 18, 1824, the son of Dr. Benjamin van der Mark and Ann Gilmore (Weir) Teel. In 1828 the family moved to Rushville, Illinois. Mrs. Teel's ill health caused the family to move to Lexington, Tennessee, in 1830, but three years later they returned to Rushville, where young Teel attended school. In 1839 he began to read law in the office of a local attorney, but the family's move to Weston, Missouri, later that year interrupted his studies. In June 1841, however, Teel was licensed to practice law in Platte City, and in 1843 he established a practice in St. Joseph. In July of that year he traveled to the Rocky Mountains to perform some legal service for the American Fur Company and was captured and held briefly held by the Yankton Sioux. In 1844 he moved to Evansville, Indiana, but, as he was not yet twenty-one, could not practice law there and so established himself as a commission merchant. On June 8, 1846, Teel enlisted in Capt. William Walker's Company K of Col. William A. Bowles's Second Indiana Infantry regiment for service in the Mexican War. He was elected the company's first sergeant and later promoted to first lieutenant. He took part in Gen. Zachary Taylor's campaign in northern Mexico and received two wounds at the battle of Buena Vista. After being discharged at New Orleans on June 28, 1847, Teel set out in November for Saltillo, Coahuila, where his father was serving as a surgeon. At the end of the war the Teel family moved to San Antonio, Texas, and subsequently to Lockhart, where, in October 1848 Teel was admitted to the bar. He married Emily F. Winans in Bastrop on April 10, 1856, and shortly thereafter moved to San Antonio, where he won a considerable reputation as a criminal attorney.
In San Antonio Teel joined the Charles Bickley Castle of the Knights of the Golden Circle. On February 16, 1861, he mustered his KGC company into state service; the unit was under Col. Benjamin McCulloch when Gen. David E. Twiggs surrendered the federal property at San Antonio to Texas state troops. Teel later sent detachments to garrison camps Hudson and Stockton and forts Clark, Duncan, and Lancaster. His company, reorganized at Fort Clark on May 1, 1861, was designated Light Company B, First Artillery, and mustered into Confederate service for twelve months. Teel was elected captain. The company was part of the force that compelled the surrender of federal troops at San Lucas Springs on May 9 and accompanied Col. John R. Baylor to Fort Bliss on July 10, 1861. During part of August Teel was commandant of Fort Fillmore, New Mexico, and later was appointed judge of the First Judicial District of Arizona, a post he held until December. He also served briefly as adjutant of the Army of New Mexico despite his hospitalization in August for "convalescent phthisis." Teel's company saw action at the battle of Valverde, where Teel was slightly wounded, and the battle of Glorieta, as well as a number of minor skirmishes in the New Mexico campaign. As a component of Col. William Steele's Seventh Texas Cavalry regiment, Teel's company was one of the last Confederate units to abandon New Mexico and far West Texas. Before retreating from Albuquerque, Teel's men buried eight of their cannons near the town plaza; in 1889 he returned to recover them. During the evacuation Teel served as regimental provost marshal. His account of the New Mexico campaign, in which he places the blame for Confederate failure squarely on the shoulders of General Henry H. Sibley, was published in the classic Battles and Leaders of the Civil War (1887–88). Teel was promoted to major of artillery on February 21, 1862. In the spring of 1862 Jordan Bennett replaced him as battery commander, and the battery was assigned to Earl Van Dorn's Army of the West, where it saw service in Arkansas, Missouri, and Mississippi. After the war Teel returned to the practice of law and gained great prominence in criminal defense. He claimed to have defended more than 700 clients charged with capital offenses and to have saved them all from execution. Teel was the father of two children. He became a Mason in 1849 but was expelled from the lodge in 1854. He died of a heart attack in El Paso on July 6, 1899, and was buried in Odd Fellows Cemetery, San Antonio.