Nebraska currently utilizes 3 area codes. When first established by AT&T and the Bell System in 1947, 402 covered the entire state of Nebraska. The most recently added was 531 in 2011 as an overlay to 402. Today, 402 is the most populated with an estimated 1.5 million of the state's 1.8 million residents.
Sources: North American Numbering Plan Administration (NANPA), telecom providers, and the U.S. Census Bureau.