Part of the larger 64,000 square mile Chesapeake Bay Watershed

Marsh Creek is a 77 square mile watershed in Adams County, PA. At the confluence with Rock Creek, Marsh Creek becomes the Monocacy River, which then drains to the Potomac River and finally to the Chesapeake Bay. The Marsh Creek Watershed headwaters begin in and near the Micheaux State Forest. Tributaries that flow into Marsh Creek include Willoughby Run, Little Marsh Creek, Mummasburg Run, Muskrat Run, Plum Run, Green Run and Poplar Spring Creek. The Marsh Creek and its tributaries flow through a variety of landscapes: orchards, farmland, villages, the Gettysburg National Military Park, commercial and industrial centers, and woodlands. Marsh Creek serves as the western boundary of Cumberland Township and separates it from both Freedom and Highland townships. The watershed portions of Franklin, Highland, Cumberland, Freedom, Hamiltonban and Butler townships, and a very small portion of Gettysburg Borough. Communities such as Orrtanna, Cashtown, McKnightstown, Knoxlynand Greenmount are also located within the watershed.

While the health and function of the Chesapeake Bay may not be of obvious concern to Marsh Creek Watershed municipal governments and citizens because it is so geographically far away and comprises a very different ecosystem. The function and health of the Bay ecosystem is a direct reflection of the health and function of each of its tributary watersheds, including the Marsh Creek Watershed.