Boston and Maine 3713, also known as the "Constitution", is the sole survivor of the "P-4a" class 4-6-2 "Heavy Pacific" type steam locomotives.

It was built in December 1934 by the Lima Locomotive Works for the Boston and Maine Railroad (B&M), hauling passenger trains around the New England region.

It was the focus of Project 3713, a partnership between the National Park Service and the Lackawanna & Wyoming Valley Railway Historical Society.

[1] These locomotives were originally built with smoke deflectors, a single air compressor mounted on their pilot deck, and a metal sky-lining shroud covering up the top of their boiler thus giving them a semi-streamlined appearance.

[1] They were assigned to haul B&M's high priority passenger trains such as the Minute Man, Alouette, Red Wing, and Flying Yankee all over the New England states.

3713 was officially named The Constitution by J. Schumann Moore, a 14-year-old student from Eastern High School in Lynn, Massachusetts.

3715 to 3719 were also named Kwasind, Rogers’ Rangers, Old North Bridge, Ye Salem Witch, and Camel’s Hump, respectively.

3713 became a stationary boiler to melt the snow and heat the passenger cars at the North Station terminal in Boston, Massachusetts.

[1] It was recalled to road service to cover for diesel locomotives during a flood, presumably in relation with the events of Hurricane Diane which affected the area at that time.

3713 ran the Steam Safari excursion round trip between Boston and Portland, Maine, and was officially retired from revenue service in July 1956.

[6][7] The locomotive was moved to the B&M’s shops in Billerica, Massachusetts for a cosmetic restoration, and then it was put on static display outside the MoS’ building.

3713 locomotive is currently being restored to operating condition through the Project3713 partnership with the Lackawanna & Wyoming Valley Railway Historical Society (L&WVRHS).

[8] The estimated restoration work cost was $1.4 million, which required repairs to the boiler, air compressors, feedwater heater, and pilot truck.