The St. Johns River is the longest river in the U.S. state of Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 and its most significant for commercial and recreational use. At 310 miles (498.9 km) long, it winds through or borders twelve counties, three of which are the state's largest. The drop in elevation from the headwaters to the mouth is less than 30 feet (9.1 m); like most Florida waterways, the St. Johns has a very slow flow rate at a third of a mile an hour (0.2 km/h), and is often described as "lazy".