US Wetlands Map: Explore National Wetlands Inventory Data by Type
This interactive US wetlands map displays wetland and deepwater habitat locations across all 50 states and US territories, using data from the National Wetlands Inventory (NWI), maintained by the US Fish and Wildlife Service. Polygons are color-coded by wetland type, and you can filter by wetland system to focus on freshwater, estuarine, riverine, or coastal habitats.
How to Use This Map
Getting Started
The map opens centered on the Mississippi River floodplain, a region rich in palustrine and riverine wetlands. Wetland polygons appear at zoom level 8 and above. If you see the “Zoom in” message, scroll in or use the + button to load wetland data.
Filters and Controls
Use the Wetland System dropdown to filter by one of the five NWI systems:
- Palustrine – inland freshwater marshes, swamps, bogs, and shallow ponds
- Estuarine – coastal salt marshes, mangroves, and tidal flats
- Riverine – river and stream channels and their banks
- Lacustrine – lakes and deep freshwater ponds
- Marine – open ocean and coastal shoreline habitats
The legend updates automatically to show only the wetland types present in the current view. Click any polygon to see its full NWI classification, including system, subsystem, class, water regime, and Cowardin attribute code.
About US Wetlands
Wetlands are transitional areas between terrestrial and aquatic systems. They provide critical ecosystem services, including flood control, water quality improvement, carbon sequestration, and habitat for migratory birds and fish. The contiguous United States has lost more than half of its original wetland area since European settlement, with the largest losses in the Midwest corn belt and Gulf coastal plain.
The National Wetlands Inventory has mapped wetland locations across the US since 1974 using aerial photography and satellite imagery. The NWI uses the Cowardin classification system, which organizes wetlands by system, subsystem, class, subclass, and modifiers such as water regime and human impact. Each polygon on this map corresponds to an NWI mapping unit, and the attribute codes in popups encode the full Cowardin classification.
Wetland coverage varies significantly by region:
- Gulf Coast – Louisiana holds the largest area of estuarine marsh in the continental US
- Prairie Pothole Region – the Dakotas and Minnesota contain millions of small palustrine wetlands critical for waterfowl
- Pacific Coast – estuarine wetlands along Puget Sound and San Francisco Bay support diverse shorebird populations
- Atlantic Coast – tidal marshes from Maine to Florida represent some of the most productive coastal ecosystems in the world
- Florida Everglades – a large freshwater marsh system with unique subtropical wetland types
Data Sources and Limitations
Wetland data is sourced from the USFWS National Wetlands Inventory, served via the Esri USA Wetlands feature service. The dataset is updated annually.
Coverage is not complete for all areas. NWI mapping has been conducted at different times and scales across the country, so some regions have more detailed or more recent data than others. The dataset does not capture all small or isolated wetlands below the minimum mapping unit for each survey. Urban development and agricultural drainage since the original survey date may mean some polygons no longer reflect current ground conditions.
Wetland polygons are displayed at zoom level 8 and above to keep map performance manageable.
Frequently Asked Questions
What are the five wetland systems in the NWI classification?
The Cowardin system used by the NWI defines five systems: Marine (open ocean), Estuarine (coastal tidal areas), Riverine (rivers and streams), Lacustrine (lakes), and Palustrine (inland freshwater marshes, swamps, and bogs). Palustrine wetlands are the most widespread type in the continental US.
What does the NWI attribute code mean?
The attribute code in the pop-up encodes the full Cowardin classification. For example, PEM1C stands for Palustrine (P), Emergent (EM), persistent emergent (1), Seasonally Flooded (C).
How often is the NWI data updated?
The Esri-hosted feature service is updated annually. The underlying NWI mapping for individual states is updated on a rolling schedule as new aerial surveys are completed. Some areas may not have been resurveyed for many years.
Can I download NWI wetlands data?
Yes. The USFWS provides free downloads of NWI data by state through the NWI Wetlands Mapper, available in shapefile, geodatabase, and other formats.
Why do some areas show no wetlands?
Wetland polygons only render at zoom level 8 and above. If you are zoomed in and still see no wetlands, the area may genuinely have few mapped wetlands, or the NWI survey for that region may be incomplete or pending an update.
