Louisiana currently utilizes 5 area codes. When first established by AT&T and the Bell System in 1947, 504 covered the entire state of Louisiana. The most recently added was 985 in 2001. Today, 318 is the most populated with an estimated 1.2 million of the state's 4.5 million residents.
Sources: North American Numbering Plan Administration (NANPA), telecom providers, and the U.S. Census Bureau.