A monument overlooking a farm field.

Marsh Creek starts as headwaters near the South Mountain and the Michaux State Forest in the far western part of Adams County. This region is part of the Blue Ridge physiographic province and contains older and harder rocks than the surrounding areas. Because the surface consists mainly of rocks resistant to weathering and erosion, the ridge commonly rises above the adjacent areas of the more readily rocks of the piedmont. The elevation of the divide at the headwaters is at 1906 feet. In the rolling hills of the Piedmont region, Marsh Creek and its tributaries wind their way down through the orchard country to the red shale region outside of Gettysburg. At the confluence located near Harney in Maryland, Marsh and Rock creeks join to form the Monocacy River. The mouth of the Marsh Creek is at an elevation of 361 ft. Marsh Creek is 27.8 miles long from headwaters to the mouth.