(Whiffletree, 13', 1971, 21-09-D) across Bittersweet Brook NE of Billerica, Billerica Township, Middlesex County, MA. Andover Rd. NE (curves E.) 0.8 miles from jct with MA3A (Boston Rd.) in Billerica to the bridge at 101. (8-7-02, N42 33.86 W71 15.39) Photo by Dan Brock.