On August 1, 1859, the Metropolitan was granted permission to add a -long branch to School Street (northwest of Brookline Village) along what was then called Washington Street. (It was soon renamed as Tremont Street east of Brookline Village; the portion between Brigham Circle and Brookline Village was renamed again as part of Huntington Avenue in 1895.) The line opened on October 26, 1859. Permission to double-track the line was given on September 9, 1879. The portion west of Brookline Village may have been intermittently operated.