Thomas J. Rabb, soldier and member of Stephen F. Austin's Old Three Hundred, was born in Fayette County, Pennsylvania, about 1801, the son of Mary (Smalley) and William Rabb. He was the brother of Andrew and John Rabb and Rachel (Rabb) Newman. All were settlers in Stephen F. Austin's original colony and for this reason received substantial land grants from the Mexican government. The family left Pennsylvania about 1803 and, after a short stay with relatives in Warren County, Ohio, reached their destination near the Mississippi River in Indiana Territory (later Illinois Territory) in 1804. They moved to Arkansas Territory in 1818. As early as 1819, while the family was living near the Red River in Arkansas Territory, Rabb made exploratory trips with his father into south central Texas in preparation for eventual settlement in the region. He accompanied his parents on their move to a chosen site in Austin's proposed colony, where they arrived in December 1821. In early 1822 Rabb and his father met with Austin on his return to Texas following the death of his father, Moses Austin. When Stephen Austin went to Mexico City to reconfirm his colonization permit, they accompanied him to San Antonio. The other members of the Rabb family had remained in Arkansas Territory; they traveled to Texas in the fall of 1823. Initially, the entire family settled on the west side of the Colorado River a short distance above the site of present La Grange. In the spring of 1824 the Rabbs decided to move farther south in the colony to escape Indian harassment. Thomas accompanied the family on this move and subsequently located near the settlement of Egypt in what is now Wharton County, an area of Austin's colony known as the District of Colorado. On July 24, 1824, he received title to his headright of one square league (about 4,500 acres) in that area. In 1824 he was appointed first lieutenant in a militia battalion organized by Stephen Austin for security of the colony. In the 1825 census Rabb is listed as a farmer and stock raiser.
On October 6, 1835, Rabb joined the volunteer army forming to intercept Mexican troops being sent into Texas to take punitive action against the colonists, and on October 28 he participated in the battle of Concepción. He was honorably discharged on November 23, 1835, and was subsequently selected by the General Council to recruit reinforcements for the newly authorized volunteer Texas army. He was elected a delegate from the Mina district to the Convention of 1836 but chose not to attend because he was engaged in raising a company of soldiers for military service. He received an appointment as captain, effective February 1, 1836, and his troops became Company F, First Regiment of the revolutionary army. On March 6 Rabb led his company into Gonzales to join other troops gathering there under the command of Gen. Sam Houston. After the fall of the Alamo he served with the army during its eastward withdrawal. On April 4, after the Runaway Scrape began, Rabb left the army, with the approval of General Houston, to rescue his family on the Colorado River from the advancing Mexican forces. He subsequently rejoined the army and was honorably discharged on August 29, 1836. He was not present at the battle of San Jacinto.
After the war Rabb moved back to his home near Egypt. He later moved to Rabb's Prairie in what is now Fayette County, where he apparently settled on a portion of the large grant that his father had received for erecting a gristmill to help feed the settlers of Austin's colony. Beginning in September 1840 Rabb served as captain of a ranger company under the command of Col. John H. Moore. In this capacity he participated in a campaign against the Comanche Indians that culminated in a Texan victory near the Red Fork of the Colorado River (near present Colorado City in Mitchell County) on October 24, 1840, thus putting an end to the Comanche uprising which had begun the previous year (see LINNVILLE RAID OF 1840). Camp Rabb, located on the Concho River within what is now either Concho or Tom Green County, was probably named for Thomas Rabb. His last recorded military service was in March 1842, when a company under his command was deployed to San Antonio to assist in repelling a raid by Mexican troops led by Gen. Rafael Vásquez. Thomas Rabb married twice. His first wife, Serena Gilbert, was the daughter of colonist Sarah Gilbert. They had three children. Serena died in 1836, soon after returning home from the Runaway Scrape. Sometime later, Rabb married a woman named Barthenia; they had two children. He died at his residence in Fayette County on October 29, 1846, and is believed to be buried near Round Top.