North of Mount St. Mary's University, US 15 meets the southern end of US 15 Business (Seton Avenue) at a superstreet intersection that also serves Old Frederick Road; U-turn ramps on either side of the intersection provide the missing movements. The U.S. Highway crosses Toms Creek and Flat Run along the eastern side of the town of Emmitsburg before its interchange with MD 140 (Main Street). MD 140 is accessed via a pair of right-in/right-out interchanges with Emmit Gardens Drive, which is unsigned MD 904H on the northbound side of US 15 and MD 904F on the southbound side. North of MD 140, the southbound direction of US 15 has a welcome center, the Mason and Dixon Discovery Center. US 15's last intersection in Maryland is with the northern end of US 15 Business (Seton Avenue) and Welty Road, which leads to Old Gettysburg Road. North of the intersection, US 15 becomes a freeway that continues across the Pennsylvania state line as the U.S. highway's bypass of Gettysburg.