Fairbury is a city and county seat of Jefferson County, Nebraska, United States. The population was 3,942 at the 2010 census. Fairbury has been closely connected with railroading for much of its history. It was founded on the projected route of a railway, and grew as a shipping center. For nearly 80 years, it was the location of the Western Division headquarters of the Rock Island Railroad. Fairbury prospered with the Rock Island, and lost business and residents as the railroad declined.