Gunpowder River, MD

The Gunpowder River is a river in Maryland, United States. It is formed by the joining of Big Gunpowder Falls and Little Gunpowder Falls. Big Gunpowder begins in the extreme southern part of Pennsylvania's York County. From there, the "Big Gunpowder" flows in a generally southeast direction through the length of Baltimore County until it reaches Joppatowne where it is joined by the "Little Gunpowder" and the Bird River becoming simply the "Gunpowder River" once it passes the Amtrak train bridge that runs from Chase to Joppa. Joppa was an important deep-water seaport and rival to the port of Baltimore in colonial American times, until sedimentation of the Gunpowder River caused by upstream development made its harbor inaccessable to large ships.

Little Gunpowder Falls, as its name implies, is much smaller. Throughout its length, it forms much of the boundary between eastern Baltimore County and western Harford County until it reaches Big Gunpowder. From there, the Gunpowder River is mainly a tidal estuary of the Chesapeake Bay that continues to form the boundary between Baltimore and Harford counties.