Historic Markers Across Florida

The St. Johns River and Lake Monroe

Marker ID:  
Location: W Seminole Blvd. (US 92), Sanford, FL
County: Seminole
Coordinates: N 28° 48.948    W 081° 16.339
  28.8158    -81.27231666
Style: Interpretative Sign **
Waymark: WMNNVN


At approximately 310 miles long, the St. Johns River is Florida's longest river. It is one of only a few rivers in the Northern Hemisphere that flows northward. The slow-moving river drops approximately thirty feet from its headwater marches in the Kissimmee Prairie in Indian River County to its mouth at the Atlantic Ocean near Jacksonville. That means the bottom drops an average of one inch per mile.

The St. Johns River is the remnant of an ancient intra-coastal lagoon system that evolved into the present day river as the sea level dropped and barrier islands formed. Today many smaller rivers feed the river within its drainage basin. These tributaries include the Wekiva River, Ecolackhatchee River and Ocklawaha River.

The St. Johns River drainage basin covers approximately 12,400 square miles, about 21 percent of the State of Florida It drains north and east central Florida, including all of Brevard, Clay, Duval, Flagler, Indian River, Nasau. Seminole, St. Johns, and Volusia counties, and portions of Alachua, Baker, Bradford, Lake, Marion, Okeechobee, Orange, Osceola and Polk counties.

The slow movement of the river does not allow pollutants to be flushed out easily. Runoff from urban and agricultural areas and discharge from water treatment plants are major sources of pollution. At times when the river is low, tides from the Atlantic Ocean may cause reverse flow, bringing salt water 161 miles upstream into Lake Monroe.

In Central Florida, the wider parts of the St. Johns River form lakes such as Lake Monroe. Named after President James Monroe, the 9258-acre lake is bound by Seminole County and Volusia County. This lake supports a variety of wildlife and provides recreational opportunities for the region. The City of Sanford sits on the southern shore of the lake.

Early on, the St. Johns River served as a vital transportation route for indigenous people and European and American settlers. It was a crucial source of shipping for produce heading north, and material goods heading to South Florida. Many port cities developed along the course of the river during the time of steamships and paddleboats. Today the St. Johns still serves as avital environmental, recreational, and ecotourism waterway with Sanford the farthest navigable upstream port.

City of Sanford