The Stellwagen Bank National Marine Sanctuary (Sanctuary) consists of an area of approximately 638 square nautical miles (NM) of Federal marine waters and the submerged lands thereunder, over and around Stellwagen Bank and other submerged features off the coast of Massachusetts. The boundary encompasses the entirety of Stellwagen Bank; Tillies Bank, to the northeast of Stellwagen Bank; and portions of Jeffreys Ledge, to the north of Stellwagen Bank.

The Sanctuary boundary is identified by the following coordinates, indicating the most northeast, southeast, southwest, west-northwest, and north-northwest points: 42°45′59.83″ N×70°13′01.77″ W (NE); 42°05′35.51″ N×70°02′08.14″ W (SE); 42°07′44.89″ W×70°28′15.44″ W (SW); 42°32′53.52″ N×70°35′52.38″ W (WNW); and 42°39′04.08″ N×70°30′11.29″ W (NNW). The western border is formed by a straight line connecting the most southwest and the west-northwest points of the Sanctuary. At the most west-northwest point, the Sanctuary border follows a line contiguous with the three-mile jurisdictional boundary of Massachusetts to the most north-northwest point. From this point, the northern border is formed by a straight line connecting the most north-northwest point and the most northeast point. The eastern border is formed by a straight line connecting the most northeast and the most southeast points of the Sanctuary. The southern border follows a straight line between the most southwest point and a point located at 42°06′54.57″ N × 70°16′42.7″ W. From that point, the southern border then continues in a west-to-east direction along a line contiguous with the three-mile jurisdictional boundary of Massachusetts until reaching the most southeast point of the Sanctuary. The boundary coordinates are listed in appendix A to this subpart.