Sabine County lay in a borderland between Spain and the United States from 1803 to 1819 and after 1820 became an entry point for many Anglo-American colonists and travelers. It was first included in the municipality of Nacogdoches, then after 1832 in the municipality of San Augustine, and on December 15, 1835, became the municipality of Sabine, taking its name from the river that forms its eastern boundary. It became a county in 1836 and was organized in 1837, with Milam as county seat from 1837 to 1858 and Hemphill since 1858. In the heart of the Pinelands, the county was home to members of the Convention of 1832, signers of the 1836 Declaration of Independence, a participant in the Battle of Coleto under Colonel James W. Fannin, Jr. whose life was spared on March 27, 1836, San Jacinto veterans, and other founders and defenders of the Republic of Texas, as well as later distinguished citizens including Texas's first U.S. Congressman, a pioneer patriot, an early missionary, and captains in the C.S.A.