Lock 0

The Tidewater Lock is a dam in Washington, D.C., west of the mouth of Rock Creek at the Potomac River, on the east side of Georgetown. Built to connect the Potomac and the Chesapeake and Ohio Canal, opened in 1831, it was a busy maritime intersection during several decades of the canal's heyday. C&O documents refer to it as Lock 0 or Tide Lock A. Today, the lock marks Milestone 0 of the National Park Service's Chesapeake & Ohio Canal trail.

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