The Yalesville Underpass is a 30 degree skew arch bridge carrying the railroad over Route 150 close to its intersection with Route 71 in Wallingford, Connecticut. Built in 1838 for the railroad by William MacKenzie, it is reported to be the first underpass in America. The arch was designed to allowed tall hay wagons to pass through but it is not wide enough for modern two-way traffic, the one-way traffic being controlled by a pair of lights. The stone structure is also one of the oldest stone railroad bridges in America.