PORT ARTHUR (formerly Prince Arthur's Landing), a town and harbour in Thunder Bay District, Ontario, Canada, on Lake Superior, and the Canadian Pacific, Grand Trunk Pacific, and Canadian Northern railways, and the lake terminus of the two latter. Pop. (1901), 3214. The lake terminus of the Canadian Pacific, originally here, has been moved to Fort William, 4 m. distant. Lumber and minerals are shipped from the surrounding district, and vast quantities of grain from the farther west.