Trinidad Coy, Cabo (corporal), scout for the Alamo defenders, and Tejano rancher, was born José Julián Trinidad de los Santos Coy at Presidio de San Juan Bautista del Río Grande, the son of soldier Pablo José Segundo de los Santos Coy and María Luisa Teresa de Rosas. Sources differ regarding his exact birthdate, which may have been January 3, 1801, but was listed in his San Antonio Daily Express obituary as January 9, 1800. The de los Santos Coy family was a military family by tradition and had served near the Río Grande since the year 1627. Nicolás de los Santos Coy, who was a soldier in the Domingo Ramón expedition, 1716–1717, was the first of the family to enter Texas. Cristóbal de los Santos Coy, who married María Curbelo, a Canary Islander, was an early school teacher in San Fernando de Béxar (now San Antonio), which was established in 1731 by Canary Island immigrants. Francisco de los Santos Coy was a soldier in Presidio San Antonio de Béxar during the time of the American Revolution, who, on the significant date of July 4, 1776, was listed on the muster roll as being "out reconnoitering for Indians." Pablo José Segundo de los Santos Coy was a cabo at Presidio de San Juan Bautista in 1805. He died about 1813, perhaps in the Battle of Medina, and the rest of the family was listed in the 1820 census of Béxar.
In 1826 Trinidad de los Santos Coy was a soldier in the Presidial Company of San Antonio de Béxar along with his brother, Antonio, and three soldiers who had married his sisters. Trinidad first married María Ignacia Gonzales in late 1829 or early 1830. They had at least two daughters—Teresa and Maria Isidora—and possibly a son, all born in San Antonio. Trinidad later married María del Refugio Vara from Zaragoza, Coahuila. They had seven sons and possibly two daughters. His mother, María Luisa Teresa de Rosas, died in San Antonio in 1834. Trinidad and Antonio took a leave of absence and appear to have ended their presidial duties by 1835. By the early 1830s, the surname of the family was shortened to Coy.
Trinidad was a volunteer soldier in the Revolutionary Army from the commencement of the Texas Revolution at Gonzales on October 2, 1835, until January 1, 1837. In December 1835 he participated as a member of the Matagorda Company which opposed Mexican general Martín Perfecto de Cós in the Siege of Béxar.
On November 26, 1911, in the San Antonio Light, Coy's son Andrés (or Andreas) gave an account of his father's reconnaissance during the siege of the Alamo. William B. Travis sent Coy to scout the location and numbers of General Santa Anna and his troops. While on this mission, Coy discovered that a boy had unwittingly fed his horse locoweed, thereby forcing Coy to borrow another pony. Mexican forces later spotted Coy and during a pursuit on horseback, Coy's mount collapsed, and he was captured. Trinidad remained a prisoner until he escaped just as the battle of the Alamo was ending and managed to arrive at the Alamo just in time to see the bodies of the Alamo defenders being burned.
In 1848 Trinidad became the foreman of the ranches San Juan Nepomuceno de la Mora (see RANCHO DE LA MORA) and El Capote, which belonged to San Antonio merchant and banker John Twohig. When Rancho San Juan Nepomuceno de la Mora was divided, Trinidad and his children received 1,000 acres from Twohig as a gift and as a business settlement. Trinidad named this property El Rancho del Paso de la Conquista, after the natural rock crossing on the San Antonio River. In 1854 Trinidad and his family continued to live at his ranch west of Conquista Crossing in the newly created Karnes County. That winter, the Coy family gave the newly arrived Polish settlers at Panna Maria several wagon loads of corn for bread and seed. In the 1860 census for Karnes County, Texas, Trinidad Coy was listed as a farmer. During the Civil War Trinidad served in the Panna Maria Greys, a home guard company. After the war he resumed farming and ranching. His sons were raised to be neighborly frontiersmen, horsemen, ranchers, policemen, and some even became gunslingers.
Trinidad retired from ranching after 1880 and moved to San Antonio. He died on December 11, 1888, and was buried in San Fernando Cemetery No. 1 in San Antonio. An obituary in the December 13, 1888, issue of the Laredo Daily Times stated that Trinidad Coy died in San Antonio and fought in all the wars of Texas from the time he was seventeen years old and was wounded thirteen times. His obituary in the San Antonio Daily Express on December 12, 1888, stated that he was born on January 9, 1800, and that he was survived by four daughters and nine sons, including Andreas, Jacobo, and Pablo Coy. Trinidad received a Texas pension for his service during the Texas Revolution. He had served in the military from 1826 to 1834 while Texas was a state of the newly established Republic of Mexico; in 1835 to 1837 and again in 1839, he served under the Republic of Texas; and he served in a home guard unit during the Civil War.
The small Karnes county community of Coy City, Texas, about ten miles southwest of Karnes City, was named in honor of the family of Trinidad Coy, whose Rancho del Paso de la Conquista was nearby. For many years the Coy family managed the extensive ranch lands of cattleman William G. Butler in western Karnes County.