I live on Sunnyside Avenue in Arlington, Massachusetts. The neighborhood was built as two subdivisions in 1948, with 42 duplexes (84 homes total). These were starter homes with 792 square feet of finished space plus a basement with a garage. I affectionately refer to them as excellent specimens of mid-century slap-up. They were constructed in the mid 20th century, and the builder just kind of slapped them up.