Chesapeake Bay, the largest estuary in the United States, is a long Mid-Atlantic waterway between Maryland and Virginia that gathers more than 150 rivers and streams across a vast drainage basin. Formed when rising seas flooded the Susquehanna River valley about 10,000 years ago, in a region also shaped by a much older impact crater, it supports diverse habitats and abundant wildlife, from fish and oysters to migratory birds. Native peoples lived along its shores for thousands of years and gave the bay its name. Long central to regional life and work, it has also suffered modern environmental damage, prompting major restoration efforts since the 1990s.