Seminary Ridge is a northern portion of the drainage divide between the Marsh Creek Watershed on the west and the Rock Creek Watershed (east). At the south end of Oak Ridge (the northernmost portion of the divide), the north-south McPherson and Seminary ridges bifurcate southward at the triple watershed point of Willoughby and Pitzer runs (southward tributaries of Marsh Creek) with a Rock Creek eastward tributary. From the triple point, Seminary Ridge extends southward to an area with eastward drainage into the Rock Cr tributary (Stevens Creek), with the borough of Gettysburg, and with the TBD. Farther south into the Gettysburg National Park, Seminary Ridge continues as far as a branch of Pitzer Run, which divides the ridgeline (), around which the drainage divide curves to the east. The ridgeline continues south of the branch, crossing the Millerstown Road. Between the Millerstown and Emmitsburg road crossings, the west side of the ridgeline is an elevated area (hornfel along the northwest edge of a diabase sheet) about 1 mile wide along the Emmitsburg Road. Along this east side of this elevated area, the ridgeline is Warfield Ridge, the southernmost portion of Seminary Ridge near the south end of the Gettysburg Battlefield. South of the tip of Seminary/Warfield Ridge tip, the Marsh/Rock creeks' drainage divide continues about 4 miles to near the Mason–Dixon line at their confluence to form the Monocacy River.