Grand Terre Island, Jefferson parish, extreme SE La., irregularly shaped island (c.6 mi/10 km long) 5 mi/8 km ENE of Grand Isle, c.45 mi/72 km SSE of New Orleans, bet. Barataria Bay (N) and Gulf of Mexico (S); 29°18'N 89°53'W. Barataria Bay lighthouse (29°16'N 89°57'W) is at SW end, near old Fort Livingston; 29°16'N 89°56'W (abandoned 1893).