The Monocacy River is one of Maryland’s most famous rivers. The river is formed by the confluence of Marsh Creek and Rock Creek, which flow out of Pennsylvania. Extending more than 58 miles, the Monocacy is the largest Potomac River tributary in Maryland. The river is known for its beauty, recreation, and also holds great significance in American history.

The Monocacy is designated as a scenic river by the State of Maryland. Approximately 42 miles of the watershed is included in the Monocacy Scenic River Water Trail. Beginning at Rocky Ridge, the trail meanders downstream to the Potomac River.

Like other rivers in the region, the Monocacy’s water quality has been degraded. Several fish kills have been recorded, along with instances of intersex in fish and other pollution-related abnormalities.

Monocacy River Fish Species

Monocacy River fish species include brook trout, brown trout, smallmouth bass, rock bass, largemouth bass, bluegill, green sunfish, redbreast sunfish, and dozens of smaller species.

The Monocacy is one of several tributaries of the Potomac that sustain populations of the northern snakehead, an invasive species of fish from Asia.

Related Information

Potomac River


Chesapeake Bay