Thomas Jamison, one of Stephen F. Austin's Old Three Hundred colonists, was probably born in Tennessee in 1792 or 1796. He was in Texas as early as August 16, 1823, when he voted in the election that made James Cummins alcalde. As one of the Old Three Hundred, Jamison, with partner Thomas Tone, received title to a sitio now in Matagorda and Brazoria counties on July 24, 1824. The census of 1826 listed Jamison as a single farmer and stock raiser. In July 1826, with a crop planted and his house almost completed, he wrote Austin about the division of the land with Tone. In 1825 or 1826 a Thomas Jamison, probably the same man, went with James Musick, Andrew Scott, and one of several contemporary John Browns on a trading expedition to the Indians of the upper Brazos River, and in 1832 a Thomas Jamison served in Aylett C. Buckner's company at the battle of Velasco. Jamison was an assistant in Matagorda County government in 1837. By 1847 he was postmaster at Sugar Land, Matagorda County, and by 1851 he was postmaster at Caney. His will was probated in 1868.