Fort George Island Cultural State Park in the context of Boat ramp

Jacksonville (US: /ˈdʒæksənˌvɪl/ JAK-sən-vil) is the most populous city proper in the U.S. state of Florida, located on the Atlantic coast of northeastern Florida. It is the county seat of Duval County, with which the city consolidated in 1968. It is the tenth-most populous U.S. city and the largest city in the Southeast, with a population of 949,611 at the official 2020 U.S. census. The Jacksonville metropolitan area, at over 1.76 million residents, is the fourth-largest metropolitan area in Florida and 38th-largest in the United States. City-county consolidation greatly increased Jacksonville's official population and extended its boundaries, placing most of Duval County's population within the new municipal limits; Jacksonville grew to 900 square miles (2,300 km). It is the largest city by total area, land and water, in the contiguous United States.

Jacksonville straddles the St. Johns River in the First Coast region of northeastern Florida, about 12 miles (19 kilometers) south of the Georgia state line (25 mi or 40 km to the urban core/downtown) and 350 miles (560 km) north of Miami. The Jacksonville Beaches communities lie along the adjacent Atlantic coast. The area was originally inhabited by the Timucua. During Spanish rule, several missions were established in the Jacksonville area; the most prominent locally was San Juan del Puerto on present-day Fort George Island, which served the Mocama Timucua. In 1564, the French founded the short-lived Fort Caroline near the mouth of the St. Johns River. During the brief period of British rule (1763–1783), a settlement developed at a narrow point on the river where cattle crossed, known as Wacca Pilatka to the Seminole and "Cow Ford" to the British. In 1822, a year after Spain ceded Florida to the United States under the Adams–Onís Treaty, in exchange for U.S. recognition of Spanish sovereignty in Texas, a platted town was established there and named for Andrew Jackson, the first military governor of the Florida Territory and the seventh president of the United States.