Horace Alsbury was born in Hopkinsville, Kentucky, in 1805. With his father, Thomas Alsbury and his brothers James and Charles, Alsbury came to Mexican Texas as part of Stephen F. Austin's Old Three Hundred. He procured title to half a league of land on the west bank of the San Bernard River on August 3, 1824.
In August 1835, likely after being at the legislature of Coahuila and Texas in Monclova, Alsbury published a handbill warning of Antonio López de Santa Anna's plans to drive Anglo-Americans from Texas. During the Siege of Bexar from November to December 1835, he was a member of Captain John York's Company. In 1836 he married Juana Navarro, the niece of then vice-governor of Texas Juan Martin de Veramendi.
On the morning of the 23rd, 1836, after learning of the Mexican Army's presence and entrusting his wife and family to the security of the Alamo and protection of James Bowie, Alsbury rode from the Alamo as one of the first messengers sent out by William B. Travis. Juana Alsbury would remain in the Alamo during the siege and final assault by Mexican forces.
On March 1, 1836 he accompanied the thirty-two Gonzales, Texas volunteers on their way to the Alamo. Two days later on March 3, 1836 he was in Gonzales, Texas with other Texas volunteers after being unable to contact James Fannin, who was expected to reinforce the Alamo.
During the Battle of San Jacinto, Alsbury, who spoke fluent Spanish, served as a spy. The day after the battle, he and five other men captured the fleeing Santa Anna. After the battle he participated in the surveillance of the retreating Mexican troops as they marched from San Jacinto toward La Bahia and then further into Mexico. He then returned to San Antonio de Bexar in May 1836 to take his wife and her young son away from the war ravaged town to Calavero Ranch on the old Goliad road, in present day Wilson County, Texas.
After the war, the Congress of the Republic of Texas recognized him for his service as a major in the infantry and also for serving as an interpreter for the post of San Antonio de Bexar. He received a land grant south of San Antonio near the site of present Von Ormy, Texas. In 1837 he was elected as the tax assessor for Bexar County, Texas. In 1838, Horace Alsbury and Joseph Baker, working as Indian agents of the Republic of Texas, led a group of men from San Antonio de Bexar on a peace mission to meet with the Comanches on the Pedernales river. They barely escaped alive, only surviving through the intervention of Francisco Antonio Ruiz, and returned to San Antonio. In 1840 Alsbury served as commander of the Federalist leader Antonio Canales Rosillo's bodyguard along the Rio Grande during the many running battles between Mexican general Mariano Arista's and Canales, during Canales’ and Samuel W. Jordan’s attempt to establish the Republic of the Rio Grande. Alsbury barely escaped alive from the conflict and then he returned to Texas.
In September 1842, Alsbury was captured when Mexican General Adrian Woll took San Antonio. Alsbury and the other were marched to San Carlos Fortress in Perote, Veracruz, where he remained until his release on March 24, 1844. Alsbury later accompanied the American army across the Rio Grande in 1846 during the Mexican-American War and he was killed in a battle, somewhere between Camargo, Chihuahua, and Saltillo, Coahuila, in June 1847.