Developers decided to follow the Patapsco River to a point near Parr's Ridge (now known as Mount Airy), where the railroad would cross a height of land and descend into the valley of the Monocacy and Potomac rivers. Further extensions opened to Frederick (including the short Frederick Branch) on December 1, 1831; Point of Rocks on April 2, 1832; and Sandy Hook on December 1, 1834. The connection to the Winchester and Potomac Railroad at Harpers Ferry opened in 1837, then the line to Martinsburg in May 1842; Hancock in June 1842; Cumberland on November 5, 1842; Piedmont on July 21, 1851, and Fairmont on June 22, 1852. The B&O reached Wheeling, West Virginia (then part of Virginia) on January 1, 1853. That would remain the terminus through the American Civil War (apart from conflict-related outages principally between Cumberland and Martinsburg during the war) until a railroad bridge could be constructed across the Ohio River.