From both the old maps and the style it seems fairly certain that this row of four identical houses dates from before 1872. On the whole they are very well preserved, with a few alterations, but nothing to change the essentials.
The larger house on the end probably dates from before 1872 as well, although it looks newer than its neighbors; its original front is mostly intact, but it has sprouted an ugly third floor that could be removed or rebuilt by some future owner.