Area code 402
Coordinates: 42°00′N 98°00′W / 42.0°N 98.0°W
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, area code 402 was split. Eastern Nebraska retained 402, and area code 308 was assigned to western Nebraska. The overall roughly diagonal dividing line runs from the southeast between Hastings and Minden north into the northern part of the state and then west towards the eastern edge of the Sandhills in the northwest of the state.
The state's two largest cities, Omaha and Lincoln, are closely located in eastern Nebraska. In comparable circumstances in Kansas, where the largest cities, Wichita, Topeka, and Kansas City are also in the eastern part of the state, a north-south split was implemented placing Wichita in one area code, and Topeka and Kansas City in another. However, in Nebraska an east-west split was implemented in which Omaha and Lincoln retained 402, while Grand Island, then the state's third-largest city, was placed in 308.
...
Wikipedia