Well-known marshes: The Florida Everglades is the single largest marsh system in the United States, occupying almost 10,000 square kilometers. Much of the land has been lost to development, but 4,200 square kilometers have been preserved, much of it as sawgrass marshes. The Everglades are threatened by altered water cycles caused by human development, drainage for development, and polluted agriculture runoff.

Learn more about Everglades National Park.