 Known for most of its length as Catoctin Mountain Highway, US 15 is the primary north–south highway of Frederick County.The highway connects the county seat of Frederick with Point of Rocks, Leesburg, Virginia, and Charles Town, West Virginia (via US 340), to the south and with Thurmont, Emmitsburg, and Gettysburg, Pennsylvania, to the north.US 15 is a four-lane divided highway throughout the state except for the portion between the Point of Rocks Bridge and the highway's junction with US 340 near Jefferson.