highway passes under the Buckingham Branch Railroad, crosses Steel Run, and passes by Fairfax Hall. US 340 passes the General Electric Specialty Control Plant and parallels the Norfolk Southern rail line north out of the city and back into Augusta County. US 340 continues north as East Side Highway, which parallels the South River and the rail line along the flank of the Blue Ridge Mountains along the eastern edge of the Shenandoah Valley. The highway crosses Sawmill Run and reduces to two lanes in the community of Dooms and crosses Mine Branch in the village of Crimora. US 340 crosses Meadows Run, Pains Run, and Still Run and enters Rockingham County at the south end of the town of Grottoes. The highway follows Augusta Avenue through the east side of the town and meets the eastern end of SR 256 (Third Street). US 340 curves northeast and meets the eastern end of SR 253 (Port Republic Road) south of Port Republic, where the South River and North River merge to form the South Fork Shenandoah River. The highway passes to the south of the historic estate Bogota and by a monument to the Battle of Port Republic at Lynnwood. US 340 closely parallels the railroad through Berrytown to the town of Elkton, where the route follows Stuart Avenue. The highway expands to a four-lane divided highway for its partial cloverleaf interchange with US 33 (Spotswood Trail) and briefly runs concurrently with US 33 Bus. from the interchange to Old Spotswood Trail, onto which the business route continues west. Elkton to Front Royal US 340 leaves Elkton along a continuation of Stuart Avenue and continues north through the Page Valley, the valley of the South Fork Shenandoah River between the Blue Ridge Mountains to the east and Massanutten Mountain to the west. The highway crosses Dry Run, passes by the historic home Bon Air, and at Verbena crosses Naked Creek into Page County. US 340 curves northwest and enters the town of Shenandoah along Fourth Street. In the center of the Shenandoah Historic District, the highway curves north onto Fifth Street. Shortly after leaving the town, US 340 crosses over Norfolk Southern's Hagerstown District rail line. The highway passes through Grove Hill and crosses over the South Fork Shenandoah River. US 340 crosses Cub Run and passes through the hamlet of Newport before meeting the southern end of US 340