Area codes 402 and 531
Area code 402 is the telephone numbering plan code for eastern Nebraska in the North American Numbering Plan. It was one of the original area codes created in 1947, and served the entire state. In 1954, this area code was split: eastern Nebraska retained 402, and western Nebraska was placed in area code 308. The roughly U-shaped 308/402 line generally runs (from south to north) northeast along the Platte River and then northwest along the eastern edge of the Sandhills.
The state's two largest cities, Omaha and Lincoln, are both in eastern Nebraska. A comparable situation existed in Kansas, where the largest cities--Wichita, Topeka and Kansas City—are all in the eastern part of the state. For this reason, a north-south split was implemented that placed Wichita in one area code and Topeka and Kansas City in another. While conventional wisdom would suggest a similar split in Nebraska that would have left Omaha in one area code and Lincoln in another, it was decided to implement an east-west split that left both cities in 402.
Due to this configuration, 402 was nearly exhausted by the end of the 20th century. Omaha and Lincoln are not only home to most of Nebraska's landlines, but also to most of the state's fax machines, cell phones and pagers. It was originally projected to exhaust in 2001, but number pooling was implemented to stave off exhaustion. In 2009, however, NeuStar projected that 402 would exhaust in 2010. Area code 531 was implemented as an overlay across the 402 area in March 2011. Although the first 531 prefix was not assigned until February 2013, ten-digit dialing has been mandatory across the entire 402 territory since the spring of 2011.
Major cities 
See also 
|Nebraska area codes: 308, 402|
|West: 308||Area codes 402/531||East: 712, 660|
|Iowa area codes: 319, 515, 563, 641, 712|
|Kansas area codes: 316, 620, 785, 913|
|Missouri area codes: 314, 417, 573, 636, 660, 816|
|South Dakota area codes: 605|