East Baton Rouge Parish (French: Paroisse de Bâton-Rouge Est) is a parish located in the U.S. state of Louisiana. The parish seat is Baton Rouge, Louisiana's state capital. As of the 2010 census, the population was 440,171. The parish has a total area of 471 square miles (1,219.9 km), of which 455 square miles (1,178.4 km) is land and 15 square miles (38.8 km) (3.21%) is water. It is the most populous parish in the state. .