The Chesapeake Bay—the largest estuary in the United States—has been shaped by both nature and people for centuries. Historically the Bay was famous for its rich oyster reefs, fish, and underwater grass that supports wildlife and local economies. Over time, however, human activities such as farming, city development, industrial discharge, and overharvesting changed the Bay’s water quality and habitats, setting the stage for long-term environmental problems that scientists and communities are still working to fix today.