The Mount Vernon Street Historic District is a historic district consisting of the even-numbered houses at 8–24 Mount Vernon Street in Somerville, Massachusetts. The district includes four modest Greek Revival houses built c. 1850, an earlier Federal period house, and a late 19th century Second Empire house, representing a progression of housing styles through the 19th century. The houses at 8, 12, 16, and 20 Mount Vernon are all well conserved Greek Revival 1+1⁄2-story buildings with side hall layout, although #12 has had synthetic siding applied. The house at #16 has preserved more of its exterior detailing than the others, while #20 is distinctive for its use of flushboard siding, giving the house the appearance of ashlar masonry work. Behind the house at #12 is a second house that is some external Greek Revival styling, but has a five bay center entrance layout more typical of the Federal period; it is known to predate the house in front of it. The duplex at 22-24 Mount Vernon has a mansard roof characteristic of the Second Empire style; its construction date is estimated to be c. 1880.