Nassau County is the northeasternmost county of the U.S. state of Florida. According to the 2020 United States Census, the county's population was 90,352. The county seat and the largest incorporated city is Fernandina Beach. Nassau County is part of the Jacksonville metropolitan area, which was home to 1,534,701 people in 2018. The county is situated in Northeast Florida with a land area of 726 square miles (1,880 km2). Population growth in the county has increased by over 28,000 residents since the year 2000 as a result of Nassau's proximity to downtown Jacksonville, new housing developments, agricultural production, tourism locations, and a diversifying tax base with new industrial and commercial companies moving to the county. Nassau County is also a popular choice of residence for mil