The St. Johns River at Jacksonville

From a marsh in Indian River County, the St. Johns River travels 310 miles northward and ends where it mixes with the Atlantic Ocean past Mayport in Duval County, the downstream end of what the water management district calls its lower basin.

The St. Johns River Water Management District calls it Florida's longest river and one of the few rivers in the United States that flows north (SJRWMD, the St. Johns River). From its source in the marshes south of Melbourne to its mouth at Mayport, the river drops less than 30 feet in total, about one inch per mile, and the district calls it one of the laziest rivers in the world. Its tea color comes from tannins released by decaying plants. As it leaves Putnam County for Clay and St. Johns counties it widens, in places to more than two miles across, before passing Mayport and mixing with the ocean. Last verified: October 18, 2026, by refetching the district's river overview, historical facts and lower basin pages, the NOAA Mayport gauge, the Corps of Engineers harbor fact sheet, the JAXPORT timeline and the Timucuan Preserve hours page.

The district divides the river into three basins. Because the water moves north, the upper basin is the marshy headwaters in Indian River and Brevard counties and the middle basin is the central Florida stretch that forms lakes Harney, Jesup, Monroe and George (SJRWMD, basins). The overview page describes the lower basin as running from Putnam County to the mouth in Duval County, and the lower basin page as running from Lake George to the river's mouth at Mayport (SJRWMD, lower basin). That page names the main contributors of pollution in the lower basin as partially treated wastewater, farm runoff and urban stormwater as well as nutrients carried down from the basins to the south.

Wildlife named by the district along the St. Johns River includes manatees, largemouth bass and other fish, crabs, shrimp and other shellfish, river otters, waterfowl, blue herons, bald eagles and alligators (SJRWMD, wildlife).

The St. Johns River takes its name from Rio de San Juan, a Spanish name drawn from the mission San Juan del Puerto near the river's mouth, after earlier Seminole Creek, Spanish and French names.

The district's historical facts page says the French established Fort Caroline in 1562 on a high bluff overlooking the river, almost 50 years before Jamestown, and that Spanish soldiers marching north from St. Augustine captured it in 1565 (SJRWMD, St. Johns River historical facts). After England acquired Florida in 1763, King George III sent botanist John Bartram to explore it, and his son William Bartram published Travels in 1791, describing a trip up the river as far south as Lake Harney.

Steamboats later made the St. Johns River a winter destination for northern visitors. By the 1860s, the same page says, several steamers made weekly round trips from Charleston and Savannah to Jacksonville, Palatka and other river settlements, and steamboat tourism stayed important to Palatka's economy until the 1920s.

The NOAA tide gauge at the Mayport Bar Pilots Dock records a mean tide range of 4.53 feet at the mouth of the St. Johns River, and the river's flow reverses with the incoming tide twice a day.

The station page also lists the gauge's position at latitude 30 degrees 23.9 minutes north and longitude 81 degrees 25.7 minutes west, and posts the day's predicted highs and lows (NOAA CO-OPS, Mayport station 8720218).

Upriver, the tide's effect reaches far beyond Jacksonville. The water management district says the incoming Atlantic tide reverses the St. Johns River's flow twice a day, that in low water the reverse flow can reach as far south as Lake Monroe, 161 miles upstream, and that sustained northeasterly winds can hold the river in reverse for many days, which makes it hard for the current to flush pollutants (SJRWMD, flow).

The federal shipping channel in the St. Johns River is kept at 47 feet from the ocean entrance to the Dames Point terminals at River Mile 13, then 40 feet to about River Mile 20, according to the U.S. Army Corps of Engineers.

The Corps' May 2025 fact sheet for Jacksonville Harbor says the harbor begins at the mouth of the St. Johns River and gives deep draft vessels access to terminals in Jacksonville (USACE Jacksonville District, Jacksonville Harbor fact sheet). Depths are measured to mean lower low water, and Cuts F and G of the West Blount Island Channel are kept at 34 feet. The project also maintains two dredged material management areas at Bartram and Buck Islands. The fact sheet lists Infrastructure Investment and Jobs Act allocations of $37,700,000 through FY23 and $37,680,000 for FY24, names the Jacksonville Port Authority at 2831 Talleyrand Avenue as sponsor, and says annual maintenance dredging continues under two active contracts. Its note that an FY26 maintenance contract was scheduled for award in December 2025 dates from May 2025 and had not been updated on the page as of October 18, 2026.

The milestones come from the port authority's timeline (JAXPORT, port history). The two agencies describe the 47-foot reach with different end points: JAXPORT says 11 miles from the sea buoy to Blount Island, and the Corps says the ocean entrance to the Dames Point terminals at River Mile 13. Both figures are given here as each agency states them.

The grounds of Fort Caroline National Memorial and Kingsley Plantation, two Timucuan Preserve sites in Jacksonville, are open from 9:00 a.m. to 5:00 p.m., Wednesday through Sunday.

The National Park Service lists these hours for the Timucuan Ecological and Historic Preserve sites in Jacksonville (NPS, Timucuan Preserve hours). The Theodore Roosevelt Area and Cedar Point are open sunrise to sunset, with Theodore Roosevelt Area restrooms open 9:00 a.m. to 4:30 p.m. The Ribault Monument, associated with Fort Caroline, is open 9:00 a.m. to 4:45 p.m., Wednesday through Sunday, and the Ribault Club, an interagency visitor center, is open Wednesday through Sunday from 9:00 a.m. to 5:00 p.m. The Timucuan Preserve Visitor Center at Fort Caroline and the Kingsley Plantation visitor contact station keep 9:00 a.m. to 4:30 p.m. hours, Wednesday through Sunday, and Kingsley admission is free.

All National Park Service areas of the Timucuan Preserve close on Thanksgiving, December 25 and January 1, and the hours page lists November 26, 2026, December 25, 2026, and January 1, 2027, as closed, with Veterans Day, November 11, 2026, on regular hours. The preserve's mailing address is 12713 Fort Caroline Road, Jacksonville, FL 32225, and its phone is 904-641-7155.