The Delaware Extension was a rail line owned and operated by the Pennsylvania Railroad in Philadelphia, Pennsylvania. The line ran from Arsenal Interlocking in West Philadelphia southeast, south, east and north to the intersection of Delaware Avenue (now Columbus Boulevard) and Dock Street. It met the West Philadelphia Elevated at Arsenal, crossed the Schuylkill River on the Arsenal Bridge, intersected with the Washington Avenue Branch, Girard Point Branch, Swanson Street Branch (twice), and Washington Avenue Branch again in South Philadelphia, and became the Delaware Avenue Branch at Dock Street.