The Union Freight Railroad was a freight-only railroad connecting the railroads coming into the north and south sides of downtown Boston, Massachusetts. Almost its entire length was along Atlantic Avenue and Commercial Street. For most of its length, the Atlantic Avenue Elevated carried passengers above. Original configuration When the line was built in 1872, each railroad had separate tracks and a separate terminal; the current union stations at North Station and South Station had not yet been built. At first, only four connections were provided. The first connection was from the Old Colony Railroad, the line to Quincy and beyond. That line crossed the Fort Point Channel a bit west of the current bridge, ending with passenger and freight terminals southwest of the current location of South Station (fully south of Kneeland Street). The beginning of the Union Freight Railroad split off the Old Colony Railroad between the bridge and the terminals, heading northeast to Federal Street and then north on Federal Street, a street that ran from the Dorchester Avenue Bridge straight to Dewey Square (the front of South Station). Continuing north, about 1/3 of the way between Essex Street and Dewey Square, the line was met with a track from the New York and New England Railroad (now the Fairmount Line). This line came over the Fort Point Channel into South Boston (where the South Boston Bypass Road runs now) and back over the channel just south of where the Summer Street Bridge is now, with a passenger depot east of Dewey Square (roughly where the north end of South Station now lies). Freight facilities were in South Boston, where the South Boston Freight Terminal still operates; the Federal Street Freight Depot was later built on the downtown side. The Union Freight Railroad connection split south from the line to the passenger depot just after crossing Fort Point Channel, and ran west to merge with the main line on Federal Street. At Dewey Square, the Union Freight Railroad continued north on Atlantic Avenue. Various track connections were provided to markets and docks on Boston Harbor. On the east side of the North End, the line merged onto Commercial Street, and turned west and continued along Causeway Street. Halfway between Beverly Street and Haverhill Street, the line curved off Causeway Street to head north between the passenger terminal of the Fitchburg Railroad and the northern freight house of the