U.S. Route 13 (US 13) is a United States Numbered Highway running from Fayetteville, North Carolina, north to Morrisville, Pennsylvania. The route runs for through the Philadelphia metropolitan area in the U.S. state of Pennsylvania. The route enters the state from Delaware in Marcus Hook, Delaware County. It continues northeast through Delaware County, passing through the city of Chester before heading through suburban areas along Chester Pike to Darby. US 13 enters the city of Philadelphia on Baltimore Avenue and runs through West Philadelphia to University City, where it turns north along several city streets before heading east across the Schuylkill River along Girard Avenue. The route turns north and heads to North Philadelphia, where it runs northeast along Hunting Park Avenue. US 13 becomes concurrent with US 1 on Roosevelt Boulevard, continuing into Northeast Philadelphia. US 13 splits southeast on a one-way pair of streets before heading northeast out of the city on Frankford Avenue. The route continues into Bucks County as Bristol Pike, heading northeast to Bristol, where it becomes a divided highway. US 13 becomes a freeway in Tullytown and continues north to its terminus at US 1 in Falls Township, near Morrisville. US 13 roughly parallels Interstate 95 (I-95) through its course in Pennsylvania.

The routing dates back to colonial times as part of the King's Highway. In the 19th century, the road was part of several turnpikes, including the Darby and Ridley Turnpike (or Chester Pike) between Chester and Darby and the Frankford and Bristol Turnpike between Philadelphia and Morrisville. In the early 20th century, these private turnpikes became public roads. US 13 was designated through Pennsylvania in 1926, running between the Delaware border in Marcus Hook and US 1 in Morrisville. The route was designated concurrent with Pennsylvania Route 91 (PA 91) between the Delaware border and Philadelphia and PA 32 between Philadelphia and Morrisville; these concurrent state route designations were removed in 1928. US 13 originally ran through Darby on Main Street and Philadelphia on Woodland Avenue, Market Street, Broad Street, Diamond Street, Front Street, Kensington Avenue, and Frankford Avenue. In the 1930s, the route was shifted to use MacDade Boulevard, Whitby Avenue, 44th Street, Powelton Avenue, 31st and 32nd streets, Spring Garden Street, Broad Street, Roosevelt Boulevard, Levick Street, and Frankford Avenue through the city; it ran concurrent with US 1 through most of the city. Between the 1930s and 1960s, three bypass routes existed for portions of US 13 between Marcus Hook and Philadelphia. The divided highway alignment between Bristol and Tullytown was completed by 1950. The US 13 freeway between Tullytown and US 1 was completed in 1955, shifting the northern terminus to its current location. This freeway was once considered to become a part of I-95 that would pass through Trenton, New Jersey, before it was decided for the Interstate to bypass Trenton to the north. A US 13 freeway was again proposed between I-95 near Bristol and Tullytown in 1969 but was ultimately cancelled. The route was shifted to use 43rd and 44th streets, Powelton Avenue, 34th Street, Girard Avenue, 33rd Street, Ridge Avenue, and Hunting Park Avenue in Philadelphia in the 1950s. US 13 was rerouted to use Church Lane and Baltimore Avenue between Yeadon and West Philadelphia in the 1960s. The route was shifted to its current alignment through Philadelphia the 1970s. US 13 was realigned through Chester in 2022, with US 13 Business (US 13 Bus.) designated onto the former alignment.

Route description Delaware County US 13 enters Pennsylvania from Delaware in the borough of Marcus Hook in Delaware County, heading northeast on four-lane undivided Post Road. From the state line, the route has a grade crossing with a railroad spur and passes through Sunoco's Marcus Hook Industrial Complex. The road narrows to two lanes and crosses a railroad spur at-grade serving the industrial complex before it heads into the commercial center of Marcus Hook as 10th Street, intersecting the southern terminus of PA 452. US 13 crosses Conrail Shared Assets Operations (CSAO)'s Linwood Track line at-grade and runs between residential areas to the north and industrial areas to the south before it heads across the Marcus Hook Creek into the borough of Trainer. The route becomes Post Road again and passes between homes and some businesses to the north and Delta Air Lines's Trainer Refinery to the south before it crosses Stoney Creek and reaches a junction with the western terminus of PA 291 and the southern terminus of US 13 Bus., where US 13 Bus. continues northeast along Post Road and US 13 turns southeast for a concurrency with PA 291 on two-lane undivided Price Street.

The road passes between homes to the northeast and industrial areas to the southwest. The two routes make a sharp curve to the northeast and become West 2nd Street, crossing into the city of Chester and running through urban residential and industrial areas. US 13/PA 291 continues northeast and becomes a five-lane road with a center left-turn lane as it passes more urban development and empty lots. The two routes come to ramps that provide access from the eastbound direction of US 322 and to the westbound direction of US 322 just northwest of where that route crosses the Delaware River on the Commodore Barry Bridge. The road passes under the western approach of the Commodore Barry Bridge carrying US 322. Following this, US 13/PA 291 passes more urban homes and businesses as it heads northwest of the Port of Chester along the Delaware River. The two routes split from West 2nd Street and continue northeast as an unnamed road, crossing Chester Creek before passing south of Chester's City Hall and north of the William Penn Landing Site. US 13/PA 291 intersects the southern terminus of PA 320 (Madison Street northbound and Upland Street southbound), at which point the road becomes East 4th Street. The road continues through commercial areas and US 13 splits from PA 291 by turning north onto two-lane undivided Morton Avenue. The road passes under Amtrak's Northeast Corridor railroad line and runs through urban areas, intersecting the northern terminus of US 13 Bus. at East 9th Street. US 13 continues through urban development, curving to the northeast.

US 13 crosses the Ridley Creek and forms the border between Ridley Township to the north and the borough of Eddystone to the south, widening to four lanes and becoming Chester Pike. The road passes a mix of homes and businesses before it comes to a bridge over Crum Creek, at which point it fully enters Ridley Township. The route passes under I-95 and continues past commercial development in the community of Crum Lynne, gaining a center left-turn lane. US 13 enters the borough of Ridley Park and passes under the Northeast Corridor near Crum Lynne station serving SEPTA's Wilmington/Newark Line before it heads into residential areas and intersects Stewart Avenue, which heads southeast to provide access to I-95. The route continues past suburban homes and businesses as a four-lane undivided road, passing to the southeast of the former Taylor Hospital. The road forms the border between Ridley Park to the north and Ridley Township to the south before it enters the borough of Prospect Park and comes to an intersection with PA 420. US 13 continues northeast through suburban areas and runs along the border between Prospect Park to the north and the borough of Norwood to the south before fully entering Norwood. The route crosses Muckinipattis Creek into the borough of Glenolden and passes under the Northeast Corridor again. The road runs past more homes and businesses and passes through a small section of the borough of Folcroft, where it crosses Hermesprota Creek, before crossing into the borough of Sharon Hill. There, US 13 passes south of Sharon Hill station which serves as the terminus of the SEPTA Route 102 trolley line before continuing past more development. The road curves north at the point it crosses over a short tunnel carrying CSX Transportation's Philadelphia Subdivision railroad line and enters the borough of Collingdale, continuing to an intersection with MacDade Boulevard.

At this point, Chester Pike splits to the east and US 13 continues north along four-lane undivided MacDade Boulevard, crossing Darby Creek into the borough of Darby. The route passes to the west of the bus terminal at SEPTA's Darby Transportation Center and curves northeast at the Main Street intersection into urban neighborhoods, narrowing to two lanes. The road passes to the south of Holy Cross Cemetery, where it enters the borough of Yeadon, before it passes through more residential areas. US 13 turns north-northwest onto Church Lane and runs through more residential neighborhoods. The route comes to a bridge over SEPTA's Media/Wawa Line west of Fernwood–Yeadon station and crosses into Upper Darby Township, where it comes to an intersection with Baltimore Pike. Here, US 13 turns east onto Baltimore Pike and runs between Fernwood Cemetery to the north and urban residential and commercial development to the south. Farther east, the road passes through a corner of Yeadon.

Philadelphia County

US 13 crosses Cobbs Creek into the West Philadelphia section of the city of Philadelphia in Philadelphia County, where the name changes to Baltimore Avenue. Immediately after crossing the creek, the road comes to the Angora Loop at 61st Street, which serves as the terminus of the SEPTA Route 34 trolley line. At this point, the trolley tracks follow Baltimore Avenue as it continues through urban neighborhoods consisting of rowhouses along with a few businesses. The road curves to the east, passing through more urban development and crossing a set of SEPTA trolley tracks at 42nd Street. The Route 34 trolley line splits from Baltimore Avenue at 40th Street, where it heads into a subway tunnel at the 40th Street Portal. The road heads into the University City neighborhood and becomes four lanes at the 39th Street/Woodland Avenue intersection, at which point it runs between the University of Pennsylvania campus to the north and the Philadelphia VA Medical Center to the south. A block later, Baltimore Avenue ends and US 13 turns north onto four-lane divided University Avenue. The route continues north through the university campus and becomes 38th Street as it reaches an intersection with Spruce Street, where a SEPTA trolley track begins to follow the northbound lanes of the road. The roadway intersects Walnut Street, which is one-way westbound and carries the westbound direction of PA 3. At this point, westbound PA 3 becomes concurrent with southbound US 13, and 38th Street continues north through commercial areas. The road crosses one-way Chestnut Street, which carries eastbound PA 3, before coming to the junction with two-way Market Street, where westbound PA 3 turns onto southbound US 13 from Market Street. US 13 continues to follow four-lane divided 38th Street north, with the SEPTA trolley track splitting west at Filbert Street. The road passes to the east of Penn Presbyterian Medical Center before it comes to an intersection with Powelton Avenue.