<P> The St. Johns River (Spanish: Río San Juan) is the longest river in the U.S. state of Florida and its most significant one for commercial and recreational use . At 310 miles (500 km) long, it winds through or borders twelve counties, three of which are the state's largest . The drop in elevation from headwaters to mouth is less than 30 feet (9 m); like most Florida waterways, the St. Johns has a very low flow rate 0.3 mph (0.13 m / s) and is often described as "lazy". Popular belief in the St. Johns area holds that it is one of the few rivers that flow north, although north - flowing rivers are common . Numerous lakes are formed by the river or flow into it, but as a river its widest point is nearly 3 miles (5 km) across . The narrowest point is in the headwaters, an unnavigable marsh in Indian River County . The St. Johns drainage basin of 8,840 square miles (22,900 km) includes some of Florida's major wetlands . It is separated into three major basins and two associated watersheds for Lake George and the Ocklawaha River, all managed by the St. Johns River Water Management District . </P> <P> A variety of people have lived on or near the St. Johns, including Paleo - indians, Archaic people, Timucua, Mocama, French and Spanish settlers, Seminoles, slaves and freemen, Florida crackers, land developers, tourists and retirees . It has been the subject of William Bartram's journals, Marjorie Kinnan Rawlings' books, and Harriet Beecher Stowe's letters home . Although Florida was the location of the first permanent European settlement in what would become the United States, it was the last U.S. territory on the east coast to be developed; it remained an undeveloped frontier into the 20th century . When attention was turned to the state, however, much of the land was rapidly overdeveloped in a national zeal for progress . The St. Johns, like many Florida rivers, was altered to make way for agricultural and residential centers . It suffered severe pollution and human interference that has diminished the natural order of life in and around the river . In all, 3.5 million people live within the various watersheds that feed into the St. Johns River . The St. Johns, named one of 14 American Heritage Rivers in 1998, was number 6 on a list of America's Ten Most Endangered Rivers in 2008 . Restoration efforts are under way for the basins around the St. Johns as Florida continues to deal with population increases in the river's vicinity . </P> <P> Starting in Indian River County and meeting the Atlantic Ocean at Duval County, the St. Johns is Florida's primary commercial and recreational waterway . It flows north from its headwaters, originating in the direction of the Lake Wales Ridge, which is only slightly elevated at 30 feet (9.1 m) above sea level . Because of this low elevation drop, the river has a long backwater . It ebbs and flows with tides that pass through the barrier islands and up the channel . Uniquely, it shares the same regional terrain as the parallel Kissimmee River, although the Kissimmee flows south . </P> <P> The St. Johns River is separated into three basins and two associated watersheds managed by the St. Johns River Water Management District . Because the river flows in a northerly direction, the upper basin is located in the headwaters of the river at its southernmost point . Indian River County is where the river begins as a network of marshes, at a point west of Vero Beach aptly named the St. Johns Marsh in central Florida . The St. Johns River is a blackwater stream, meaning that it is fed primarily by swamps and marshes lying beneath it; water seeps through the sandy soil and collects in a slight valley . The upper basin measures approximately 2,000 square miles (5,200 km); the St. Johns transforms into a navigable waterway in Brevard County . The river touches on the borders of Osceola and Orange Counties, and flows through the southeast tip of Seminole County, transitioning into its middle basin a dozen miles (19 km) or so north of Titusville . </P>

Where does the st. johns river begin and end