Designated an American Heritage River by President Clinton in 1997, the St. Johns River is one of a kind. Its unique ecosystem has a diverse mix of flora and fauna from its headwaters to its mouth.

The river flows over 310 miles, from its headwaters at St. Johns Marsh near Fellsmere, Florida to the Atlantic, making it the longest river in Florida and the longest river in the US to flow north.

The St Johns Marsh, near Fellsmere, is generally considered the headwaters of the St. Johns River. This is where the water flow ‘officially’ becomes the St Johns River. The source creek to this water body though, is "Ft. Drum Creek" (named for a nearby Seminole Indian Wars fort). The creek actually begins in Ockeechobee County and flows northward before spreading out into the saw grass prairies south of Blue Cypress Lake.

The Upper basin is the marshy headwaters region in the most southern stretch of the river, located in East Central Florida.

In the Middle basin, the river widens into Lake Harney, then Jesup, then Monroe, flowing north through Central Florida. The dredged and marked channel of the river ends in the northern part of this basin, at the town of Sanford on Lake Monroe. This keeps larger boats from traveling into the upper river, where the channels are unmarked and more shallow.

The Lower basin is the Northeast Florida stretch of the river, from just north of the confluence of the Ocklawaha River to the River’s mouth at Mayport. This stretch of the river is characterized by heavy residential and industrial development, especially from Green Cove Springs north. The Lower basin consists of a 1.8 million acre drainage basin, and 115 square miles of surface water.

The Lake George basin is the area around the largest of the St Johns lakes, between the entry points of the Wekiva and Ocklawaha rivers, both major tributaries to the St Johns.

The Ocklawaha River basin encompasses the watershed of the Ocklawaha River, the primary tributary to the St Johns, which flows from Hog Valley to Welaka.

The St. Johns River is an ancient intracoastal lagoon system. It was formed approximately 100,000 years ago after land rose along the coast and trapped a portion of the sea inland. However, the river did not take on its current form until only about 5,000-7,500 years ago, after the sea began to rise at the end of the last ice age.

The St Johns is a tannic, or black water river, due to its golden tea-colored water. This coloration is a natural result of the tannic acid released into the water from decaying organic matter such as leaves.

The St. Johns is referred to as a brackish system because it is not entirely made of freshwater like most rivers. It receives salt from two sources. One source is from ancient seawater pockets in the Floridian Aquifer, which releases salt water through various springs (Salt Springs, etc). The second is from the Atlantic Ocean that carries seawater in as far as Lake George during normal conditions, and even to Lake Monroe or further during drought conditions. The amount of freshwater moving northward out of the marshes (less during drought) determines the amount of seawater that can push in southward from the Atlantic Ocean, thus defining the brackish water zone.

In the past, wetlands were believed to be of little value, and were drained for other uses. Florida, with an estimated historical coverage of 54% wetlands, has lost over half of these precious ecosystems. Wetlands aid in the removal of pollution, flood control, and erosion prevention, not to mention wildlife habitat rich in biodiversity. Between the 1930s and 1970s, the St Johns River lost over 60% of its nearly 290,000 acre wetland coverage, leading to increased pollution and flooding problems, as well as precious habitat loss. The largest uninterrupted wetland habitat in the St Johns basin is the Three Forks Marsh and Blue Cypress Conservation areas, with over 10,000 acres. Nine distinct wetland habitats can be found within the St Johns River basin, including hardwood swamps, deep marshes, and seepage slopes.

The St. Johns River System encompasses numerous habitats & ecosystems, including estuaries and various wetlands. It is these areas especially where animals come to mate, raise young, feed, and live. Many species that do not normally live in the river utilize it as a highway to a specific destination or as a residence for a specific part of their life cycle. For example, the American Eel travels to our river all the way from the Sargasso Sea in order to mature. This is why the St Johns River system has such incredible biodiversity (high concentration of many species).

The St. Johns River is home to over 180 different species of fish.

Florida has the second largest population of bald eagles of any state in the country, and nearly 70 percent make their nests along the St. Johns River.

The only Florida stork species, the Wood Stork Mycteria americana, calls the St. Johns River home.

Many marine mammals are found in the river such as the West Indian Manatee, Bottlenose Dolphin, Tiger Shark, Bull Shark, and Atlantic Stingray.

Any non-native plant or animal that adversely affects the habitats they invade economically, environmentally or ecologically.

Unfortunately, there are many species of plants and animals brought to our area by people, some who don’t even know they have brought an invader. Some of these species are good hitchhikers that attach themselves to boats and get a free ride to our ecosystem, such as the green mussel, which is thought to have arrived via the ballast water of ships. Although, people knowingly bring some species for a particular purpose without knowing the impact on our local ecosystem such as Nutria that was brought to Florida for the fur trade.