Bat·on Rouge (bāt'n rōōzh') The capital of Louisiana, in the southeast-central part of the state on a bluff above the Mississippi River. Founded in 1719 as a French fort, it became the state capital in 1849 and was captured (May 1862) by Union admiral David Farragut during the Civil War. It is a major port of entry and oil-refining center. Population: 230,000.