The portion of Beacon Street west of Kenmore Square was laid out in 1850, intersecting with Avenue Street (now the Allston portion of Commonwealth Avenue), Mill Dam Road (now Brookline Avenue), and Western Avenue, a road traversing the Back Bay mill dam in approximately the modern location of Beacon Street. The Boston and Worcester Rail Road and the Charles River Branch Railroad combined here to cross the Back Bay on a separate railroad bridge, making a beeline for the Leather District. The railroad lines still exist on more or less their original alignments, with the city developing around them. Minor adjustments have been made for the construction of South Station, what is now the MBTA Green Line, and the Massachusetts Turnpike.