Located on the east side of the road just south of its junction with Wakefield Street, it is a granite slab with a rounded top that is about 2.5 feet (0.76 m) in height (including the buried portion).

It is marked "B / 12 / M", denoting the distance along what was historically the post road between Boston and Haverhill.

Similar markers are found in neighboring Wakefield.

[2] The marker was added to the National Register of Historic Places in 1985.

[1] This article about a National Register of Historic Places listing in Reading, Massachusetts is a stub.