Jacksonville is the largest city in the U.S. state of Florida in terms of both population and land area, and the largest city by area in the continental United States. It is the county seat of Duval County, with which the city government consolidated in 1968. The consolidation gave Jacksonville its great size and placed most of its metropolitan population within the city limits; with a population of 821,784, it is the most populous city proper in Florida and the eleventh most populous in the United States. Jacksonville is the principal city in the Greater Jacksonville Metropolitan Area, with a population of 1,313,228.

During the American Civil War, Jacksonville was a key supply point for hogs and cattle being shipped from Florida to aid the Confederate cause. The city was blockaded by Union forces, who gained control of the nearby Fort Clinch. From 1862, they controlled the city and most of the First Coast for the duration of the war. Though no battles were fought in Jacksonville, the city changed hands several times. Warfare and the long occupation left the city disrupted after the war.

During Reconstruction and the Gilded Age, Jacksonville and nearby St. Augustine became popular winter resorts for the rich and famous. Visitors arrived by steamboat and later by railroad. President Grover Cleveland attended the Sub-Tropical Exposition in the city on February 22, 1888 during his trip to Florida. This highlighted the visibility of the state as a worthy place for tourism. The city's tourism, however, was dealt major blows in the late 19th century by yellow fever outbreaks. In addition, extension of the Florida East Coast Railway further south drew visitors to other areas. From 1893 to 1938 Jacksonville was the site of the Florida Old Confederate Soldiers and Sailors Home with a nearby cemetery.

Jacksonville, like most large cities in the United States, suffered from negative effects of rapid urban sprawl after World War II. The construction of highways led residents to move to newer housing in the suburbs. After World War II, the government of the city of Jacksonville began to increase spending to fund new public building projects in the boom that occurred after the war. Mayor W. Haydon Burns' Jacksonville Story resulted in the construction of a new city hall, civic auditorium, public library and other projects that created a dynamic sense of civic pride. However, the development of suburbs and a subsequent wave of middle class "white flight" left Jacksonville with a much poorer population than before.

Downtown Jacksonville has a skyline with the tallest building being the Bank of America Tower, constructed in 1990 as the Barnett Bank Center. It has a height of 617 ft (188 m) and includes 42 floors. Other notable structures include the 37-story Modis Building (with its distinctive flared base making it the defining building in the Jacksonville skyline), originally built in 1972-74 by the Independent Life and Accident Insurance Company, and the 28 floor Riverplace Tower which, when completed in 1967, was the tallest precast, post-tensioned concrete structure in the world.

The city center includes the Jacksonville Landing and the Jacksonville Riverwalks. The Landing is a popular riverfront dining and shopping venue, accessible by River Taxi from the Southbank Riverwalk. The Northbank Riverwalk runs 2.0 miles (3.2 km) along the St. Johns from Berkman Plaza to I-95 at the Fuller Warren Bridge while the Southbank Riverwalk stretches 1.2 miles (1.9 km) from the Radisson Hotel to Museum Circle.

Adjacent to Museum Circle is St. Johns River Park, also known as Friendship Park. It is the location of Friendship Fountain, one of the most recognizable and popular attractions for locals as well as tourists in Jacksonville. This landmark was built in 1965 and promoted as the “World’s Tallest and Largest” fountain at the time.

There are also several historical properties and items of interest in the city, including the Klutho Building, the Old Morocco Temple Building, the Palm and Cycad Arboretum, and the Prime F. Osborn III Convention Center, originally built as Union Station train depot. The Jacksonville Historical Society showcases two restoration projects: the 1887 St. Andrews Episcopal Church and the 1879 Merrill House, both located near the sports complex.

Jacksonville is home to one major league sports team, the Jacksonville Jaguars of the National Football League (NFL). Jacksonville is also home to several minor league-level teams.

Two of Jacksonville's high schools, Stanton College Preparatory School and Paxon School for Advanced Studies regularly appear at the top of Newsweek magazine's annual list of the country's top public high schools, coming in respectively at #3 and #8 in the 2010 edition. Five other schools, Douglas Anderson School of the Arts (#33), Mandarin High School (#97), Fletcher High School (#205) Sandalwood High School (#210), and Englewood High School (#1146) were also included in the list.