The Angle Tree Stone is a historic boundary marker astride the border of North Attleboro, Massachusetts and Plainville, Massachusetts. The slate marker was built in 1790 by a father and son team of gravestone makers. The stone was added to the National Historic Register in 1976. The stone replaced the "Angle Tree" from the 17th century, which was a surveying landmark for the boundary between Bristol and Norfolk counties, and also between North Attleborough and Plainville, Massachusetts. The county border is a straight east-west line coming from Cumberland, Rhode Island to the site of the tree (now the stone) and then turning at an angle (hence the "angle tree" designation) and running in a straight line from there almost to Massachusetts Bay near Cohasset.