Shark River Slough provides the primary source of water to Everglades National Park, and lies mostly within Everglades National Park boundaries. Shark River Slough is a natural wetland depression that contains organic sediments made up of both shallow and deep peats. Historically, the Shark River Slough drainage originated in Water Conservation Area 3. Water flowed southeastward in an arc that swept through the area that is now called the east Everglades and curved back to the west to flow down the main channel of the slough through the heart of Everglades National Park at the Shark River Valley. The main portions of the northern slough are contained in both Everglades and the east Everglades. The slough is presently divided in the northern portion by the levee L-67E. The restoration of the historic structure and function of the Shark River Slough is critical for the restoration of Everglades National Park.