Atlantic Avenue is a street in downtown Boston, Massachusetts, partly serving as a frontage road for the underground Central Artery (I-93) and partly running along the Boston Harbor. It has a long history, with several relocations along the way. History What is now Atlantic Avenue was once part of Broad Street, only existing from the road still known as Broad Street south to Dewey Square (the front of South Station. Federal Street (which now only goes north from Dewey Square) continued south from Dewey Square through the current location of South Station to the Federal Street Bridge (now the Dorchester Street Bridge) and on to South Boston and points south. From 1868 to 1874, the section north of Broad Street was built, taking it into Commercial Street, with which it formed a waterfront route around the North End, and the portion of Broad Street south of the new road was renamed Atlantic Avenue. This new alignment took it across the middle of several former wharves, notably Long Wharf, and the water west of Atlantic Avenue was filled in. The Union Freight Railroad was completed in 1872, taking freight between the lines on the north and south sides of downtown, and running along the middle of the full length of Atlantic Avenue. In 1899, South Station opened, and as part of that project Federal Street was closed south of Dewey Square, and Atlantic Avenue was extended south along a new alignment on the west side of South Station. The Union Freight Railroad, which had used Federal Street, was also realigned onto the new alignment. Just south of Kneeland Street, the railroad continued straight but Atlantic Avenue had a quick S-curve to shift to the west side of the railroad, where it slowly rose and then turned southeast onto the Atlantic Avenue Viaduct over the full approach to South Station (the Boston and Albany and New York, New Haven and Hartford railroads), which after crossing the railroads immediately turned back to the south and crossed the Fort Point Channel. The road ended at the large intersection of Dorchester Avenue, Foundry Street and West First Street, serving the same purpose as Federal Street - taking vehicles to this intersection from Dewey Square. The viaduct was gone by 1923, and Atlantic Avenue was truncated to just south of Kneeland Street at the S-curve. Traffic formerly using Atlantic Avenue to South Boston now used Dorchester