The Isthmus of Chignecto is an isthmus bordering the Maritime provinces of New Brunswick and Nova Scotia that connects the Nova Scotia peninsula with North America. The isthmus separates the waters of Chignecto Bay, a sub-basin of the Bay of Fundy, from those of Baie Verte, a sub-basin of the Northumberland Strait that is an arm of the Gulf of St. Lawrence. The isthmus stretches from its northerly point at an area in the Petitcodiac River valley near the city of Dieppe, New Brunswick to its southerly point at an area near the town of Amherst, Nova Scotia. At its narrowest point between Amherst and Tidnish, the isthmus measures 24 kilometres wide. Because of its strategic position, it has been important to competing forces through much of its history of occupation. The name "Chignecto" derives from the Mi'kmaq name Siknikt, meaning "drainage place"; the name of the Mi'kmaq District where the isthmus is located. Geography The majority of the lands comprising the isthmus have low elevation above sea level; a large portion comprises the Tantramar Marshes, as well as tidal rivers, mud flats, inland freshwater marshes, coastal saltwater marshes, and mixed forest. Several prominent ridges rise above the surrounding low land and marshes along the Bay of Fundy shore, namely the Fort Lawrence Ridge (in Nova Scotia), the Aulac Ridge, the Sackville Ridge, and the Memramcook Ridge (in New Brunswick). In contrast to the Bay of Fundy shoreline in the west, the Northumberland Strait shoreline in the east is largely forested, with serpentine tidal estuaries such as the Tidnish River penetrating inland. The narrowest point on the Northumberland shoreline is opposite the Cumberland Basin at Baie Verte. If sea levels were to rise by 12 metres, the isthmus would be flooded, effectively making mainland Nova Scotia an island. Transportation As the Isthmus of Chignecto was a key surface transportation route since the 17th century, French and later British colonists built military roads across it to the Tantramar Marshes and along the strategic ridges. In 1872, the Intercolonial Railway of Canada constructed a mainline between Halifax, Nova Scotia and Moncton, New Brunswick across the southern portion of the isthmus. It skirted the edge of the Bay of Fundy while crossing the Tantramar Marshes between Amherst, Nova Scotia and Sackville, New Brunswick. In 1886 a railway line was built from Sackville across the isthmus to Port Elgin and on to Cape Tormentine.