Jefferson County is a county in the Coastal Plain or Gulf Prairie region of Southeast Texas. The Neches River forms its northeastern boundary. The county was named for U.S. president Thomas Jefferson. The county seat is Beaumont, which is also the largest city within the county.
The county was established in 1835 as a municipality of Mexico, which had gained independence from Spain. Because the area was lightly settled, the Mexican government allowed European Americans from the United States to settle here if they pledged loyalty to Mexico. This was organized as a county in 1837 after Texas achieved independence as a republic. Texas later became part of the US.