The ease of transportation via the Old Colony Railroad revolutionized Dorchester in the period between 1850 and the Civil War and brought a residential building boom that lasted the next seven decades. The town was annexed to the city of Boston in 1870, and by the turn of the century, Dorchester was one-fifth of the entire city. By the time of the Great Depression, the three-decker, Dorchester’s unique contribution to American architecture, was a trademark of the community. Dorchester, part of the Then & Now series, places vintage images alongside contemporary photographs to explore the history of this community’s public schools, places of worship, transportation, streetscapes, and historic houses.