The Dorchester Railroad and Dorchester Extension Railroad was a horse car line in Boston, Massachusetts in the late 19th century, running from downtown south to Milton, mostly via Dorchester Avenue (the old Dorchester Turnpike). For several years, it was operated by Gore, Rose and Company, owned by David Gore and George Rose, because the original company could not afford to run it.
The Dorchester Avenue Railroad was chartered April 29, 1854, opened in spring 1857, and bought by the Dorchester Railroad (chartered April 29, 1855) in January 1858. The Dorchester Extension Railroad was chartered February 18, 1855. Both were leased to Gore, Rose and Company, which operated the line from June 1, 1858 to 1862.