Meridian, First or Principal
The First or Principal Meridian is the line of longitude forming the main backbone of the Dominion Lands Survey System - a plan devised in 1869 for the subdivision of the territory about to be purchased by the federal government from the Hudson's Bay Company into a rectangular system of square townships numbered northerly from the FORTY-NINTH PARALLEL and east and west of a given meridian. The Principal Meridian, sometimes referred to as the Winnipeg Meridian, ran northward from a point on the 49th parallel 10 miles (16 km) west of Pembina, where astronomical observations had been made to determine the exact position of the parallel in that location. The point was selected to avoid the settled cultivated areas taken up along the Red River prior to the survey. It has a longitude of 97°27´28´ west. The other initial meridians are spaced at intervals of about 4° of longitude and are numbered westerly and easterly from the Principal Meridian.