stop on the Broad Street line). The Market Street tunnel continues east to Front Street and then turns north, where it rises in the median of I-95. The rail line and freeway share an elevated embankment for about , including Spring Garden station (which replaced Fairmount station on the Frankford Elevated in 1977). The line then heads under the southbound lanes and over Front Street for about a mile on an elevated structure. The elevated structure then turns northeast onto Kensington Avenue, which after about , merges with Frankford Avenue (which the line follows to its end). Just north of Pratt Street, a curve to the north brings the line to its terminus at the Frankford Transportation Center, which replaced the original Bridge & Pratt Streets terminal. History Original subway and expansion The original subway tunnel from City Hall to the portal at 23rd Street, as well as the bridge to carry the line across the Schuylkill River, just north of Market Street, were built from April 1903 to August 1905. Construction on the Market Street Elevated west from this point began In April 1904, and the line opened on March 4, 1907, from 69th Street Terminal to a loop around City Hall at 15th Street. The line was elevated west of the river and underground east of the river. The tunnel was also used by streetcar lines, now SEPTA's subway–surface lines, that entered the line just east of the river and turned around at the City Hall loop. Philadelphia was unusual in that the construction of its initial downtown subway was undertaken using PRT (Philadelphia Rapid Transit Co.) private capital only, with no contribution from public funds. Extensions took the subway east to 2nd Street on August 3, 1908, and via a portal at 2nd street and several elevated curves it reached the Delaware River between Market Street and Chestnut Street on September 7, 1908. The Delaware Avenue Elevated (also called the Ferry Line, because of the multiple ferries across the river) opened on October 4, 1908, as a further extension south along the river to South Street. The only two stations on this extension were Market–Chestnut and South Street. The total cost ("road and equipment expenditures") of the Market Street subway and elevated was . The "first operating section" of the Frankford Elevated was planned to extend from Arch Street (connection with PTC Market Street line) to Bridge