Florida Everglades Geography — Florida

The Florida Everglades is a subtropical wetland ecosystem occupying the southernmost portion of the Florida peninsula. Before large-scale drainage began in the late 19th century, the system covered approximately 10,000 square kilometers — roughly one-third of the lower Florida peninsula — extending from the south shore of Lake Okeechobee southward to the mangrove estuaries of Florida Bay and the Gulf of Mexico, as documented by the South Florida Water Management District (SFWMD). The SFWMD describes the historical extent as approximately 40 miles wide by 100 miles long, covering nearly 11,000 square miles of South Florida.

Today, drainage and development have reduced the surviving wetlands to roughly half that original extent. The managed Everglades covers approximately 2 million acres, making it the largest subtropical wetland in the United States, according to the National Wildlife Federation. The U.S. Geological Survey places the full Kissimmee-Okeechobee-Everglades watershed at approximately 28,000 square kilometers, a corridor that supports a human population exceeding 5 million and supplies drinking water for more than 7 million Floridians. The Everglades is the only place on Earth where American alligators and American crocodiles coexist in the wild, as noted by the SFWMD.

The geological foundation of the Everglades consists primarily of limestone — a sedimentary rock composed of calcium carbonate — which rarely crops out at the surface because of overlying wetlands and organic peat. The NPS Geodiversity Atlas identifies the Pliocene Tamiami Formation, a fossiliferous carbonate-siliciclastic mixture, as the oldest unit exposed near the park surface. Above it lie the Pleistocene Miami Limestone in the northeastern sector and the Key Largo Limestone along the Florida Keys margin. The entire region falls within the Atlantic Coastal Plain physiographic province, which the NPS describes as geologically young and underlain by Cenozoic sedimentary deposits.

Hydrology defines the Everglades as much as geology does. The Kissimmee River drains southward into Lake Okeechobee — a lake measuring 730 square miles with an average depth of 9 feet — from which water historically spread as a continuous sheet across the low-gradient basin. UF/IFAS Publication UW199 records that the historical sheet flow traveled at approximately 34 meters per day across a basin 48 kilometers wide, with water averaging between 15 centimeters and 1 meter in depth. The gradient from Lake Okeechobee to Florida Bay was less than 4.5 centimeters per kilometer — one of the lowest elevation gradients of any river system on Earth, as noted in a peer-reviewed study published in Urban Ecosystems (Springer). The USGS associates this landscape with the Seminole name Pa-hay-Okee and with conservationist Marjory Stoneman Douglas, whose description of the system as the River of Grass became the defining phrase for its sheet-flow character.

The USGS identifies nine primary habitat types within Everglades National Park: hardwood hammocks, pine rocklands, mangrove forests, freshwater sloughs, freshwater marl prairies, cypress swamps, coastal prairies, marine and estuarine communities, and open water. Hardwood hammocks are dense shade-tree forests elevated slightly above the surrounding marsh; pine rocklands are fire-dependent pinelands rooted directly in exposed limestone substrate. Everglades National Park contains the largest contiguous stand of protected mangroves in the western hemisphere, according to the USGS.

The two dominant freshwater landscape types are the sawgrass plains in the northern reaches and the ridge-and-slough landscape in the center and south, as described by UF/IFAS. The ridge-and-slough landscape consists of patterned peatlands with alternating elevated ridges and water channels, a spatial patterning that was maintained by the historical sheet flow. Sawgrass (Cladium jamaicense) dominates in slowly moving water and gave rise to the River of Grass description. The SFWMD documents the Everglades as supporting dozens of federally threatened and endangered species, including the Florida panther, the American crocodile, the snail kite, and the wood stork.

The park supports more than 40 mammal species and 27 snake species within its boundaries alone, according to the USGS. Florida Bay, connected to the Everglades by freshwater sheet flow, is covered with seagrass beds and functions as a nursery for fish and a feeding ground for some of the largest wading-bird colonies in North America, as documented by the National Park Service.

The Everglades system is concentrated entirely in southern Florida. The marsh proper lies south of Lake Okeechobee, bounded by the Miami metropolitan area along the Atlantic Coastal Ridge to the east, the Ten Thousand Islands and Gulf of Mexico coast to the west, and Florida Bay and the Florida Keys to the south. The system encompasses portions of Miami-Dade, Monroe, and Collier Counties, as identified by the NPS Geodiversity Atlas.

The Northern Everglades and Estuaries Protection Program (NEEPP), enacted by the Florida Legislature in 2007, extends the recognized protected zone northward to encompass Lake Okeechobee, the Caloosahatchee River Watershed to the west, and the St. Lucie River Watershed to the east, reflecting the functional hydrologic connectivity from the Kissimmee chain of lakes southward. The Florida Geographic Information Office maintains the authoritative spatial boundary dataset for these northern and southern Everglades zones.

Within the southern extent, the landscape grades from freshwater sawgrass marsh and ridge-and-slough patterned wetlands in the north and center to freshwater marl prairies in the interior, then to mangrove estuaries at the coast and the open waters of Florida Bay. Big Cypress National Preserve, immediately northwest of Everglades National Park, represents a distinct but functionally related landscape of cypress domes and strands that contributes water to the broader system. The eastern flank of the Everglades transitions abruptly into the Miami metropolitan area, while the western boundary faces the Gulf of Mexico coast.

Everglades National Park was authorized by Congress in 1934 and formally established on December 6, 1947. It encompasses 1,508,976 acres across Monroe, Miami-Dade, and Collier Counties, according to the NPS Geodiversity Atlas. The park was the first national park in the United States established primarily to protect biodiversity rather than scenic landscape features. It is also identified by the National Park Service as the largest subtropical wilderness in North America.

The park holds three simultaneous international conservation designations, making it the only site in the United States to carry all three. The UNESCO World Heritage Centre inscribed Everglades National Park on the World Heritage List in 1979, recording a total area of 610,670 hectares. UNESCO designated the park a Man and the Biosphere Reserve in 1976. The Ramsar Sites Information Service records the park's designation as a Wetland of International Importance on June 4, 1987, covering 610,497 hectares; the site is also listed on the Ramsar Montreux Record, which flags wetlands requiring priority conservation attention. The NPS documents the park as the center of a complex of federal and state protected areas across South Florida.

The Comprehensive Everglades Restoration Plan (CERP), authorized by the Water Resources Development Act of 2000, is described by the SFWMD as the single largest ecosystem restoration program underway in the South Florida Ecosystem. CERP is structured around restoring the quantity, quality, timing, and distribution of water across 2.4 million acres of south Florida. It operates as a cost-sharing partnership involving the U.S. Army Corps of Engineers (USACE), the Department of the Interior, the State of Florida, tribal governments, and local agencies.

In October 2024, the USACE Jacksonville District awarded three contracts totaling $2,872,795,350 — the largest civil works stand-alone contract in Jacksonville District history — for CERP projects targeting increased water storage and resilience in the Central Everglades and the Indian River Lagoon, funded in part by a $1.1 billion investment from the federal Infrastructure Law, according to the USACE Jacksonville District report.

A key CERP component, the Everglades Agricultural Area (EAA) Reservoir Project, reached two milestones in the 2024–2025 period. In January 2024, the project's 6,500-acre Stormwater Treatment Area began filling for the first time, according to the SFWMD. In November 2025, the SFWMD broke ground on the EAA Reservoir Inflow Pump Station, a facility designed to move approximately 3 billion gallons of water per day from Lake Okeechobee southward into the reservoir — a volume intended to redirect water that would otherwise flow to the Caloosahatchee and St. Lucie estuaries.

The Everglades connects directly to Florida's water supply infrastructure through the Biscayne Aquifer, which shares the Atlantic Coastal Plain's limestone karst foundation and supplies municipal drinking water to South Florida's densely populated coastal communities. The USGS identifies the Greater Everglades watershed as the primary drinking water source for more than 7 million Floridians, making ecosystem health inseparable from regional water security.

The Kissimmee-Okeechobee-Everglades hydrologic corridor links Central Florida land use directly to South Florida water quality, tying Everglades geography to the state's agricultural policy — particularly sugar production in the Everglades Agricultural Area, which lies between Lake Okeechobee and the northern boundary of the marsh. The mangrove coastlines and Florida Bay connect to Florida's commercial and recreational fisheries sectors. Endangered species documented within the system — the Florida panther, the American crocodile, and the snail kite — fall under Florida Fish and Wildlife Conservation Commission management across multiple regions of the state.

Big Cypress National Preserve and Biscayne National Park form a contiguous protected-lands complex around the Everglades core, making South Florida one of the largest concentrations of federally protected land in the eastern United States, as documented by the National Park Service. The system also provides critical flood control and storm surge buffering for densely populated coastal counties in Miami-Dade, Broward, and Monroe.