re: Why is Lake Pontchartrain called a "lake"?

Looking at your your posted map lets have some history of the War of 1812. The Opening of Rigolets Pass to Lake Borgne is today the L&N Railroad Bridge. The island to the east is known as Pea Island. The British navys ocean going ships were to big for Lake Borgne and anchored between Ship Island and the Chandeleur Islands. The British army offloaded their troops and equipment on barges and were rowed to Pea Island as a staging area in preparation for the battle in Chalmette. American frigates fought the Brits in Lake Borgne but were boarded and captured. The British troops from the West Indies didn't survive the cold any many froze to death. Possibly buried on Pea Island. From the Pea Island staging area they rowed the barges across Lake Borgne to Bayou Bienvenue to move onto Chalmette.

Every time you fish Lake Borgne and the Rigolets think of the battle that was fought there.

At the Rigolets opening to Lake Pontchartrain are bricks under the water known to fisherman as Hospital Wall. This is remains of Fort Coquilles. Fort Pike was built later south of Highway 90.

Enough of todays history lesson.