Southwest Philadelphia is a section of Philadelphia, Pennsylvania, United States. The section can be described as extending from the western side of the Schuylkill River to the city line, with the SEPTA. The northern border is defined by the Philadelphia City Planning Commission as east from the city line along Baltimore Avenue moving south along 51st Street to S…Southwest Philadelphia is a section of Philadelphia, Pennsylvania, United States. The section can be described as extending from the western side of the Schuylkill River to the city line, with the SEPTA. The northern border is defined by the Philadelphia City Planning Commission as east from the city line along Baltimore Avenue moving south along 51st Street to Springfield Ave. It follows the train tracks until 49th Street. From 49th and Kingsessing Ave the line moves east along Kingsessing Ave. The line then moves south along 46th St to Paschall Ave where it jogs to join Grays Ferry where the line runs to the Schuylkill River.