Lake Pontchartrain [SEP] named after
defined in 1979 (see list of parishes in Louisiana).
The lake is crossed by the Lake Pontchartrain Causeway, the longest continuous bridge over water in the world.
Toponymy.
Lake Pontchartrain is named for Louis Phélypeaux, comte de Pontchartrain. He was the French Minister of the Marine, Chancellor, and Controller-General of Finances during the reign of France's "Sun King", Louis XIV, for whom the colony of "La Louisiane" was named.
The name Pontchartrain itself comes from the
de Maupeou. They had one son, Jérôme Phélypeaux (1674–1747), comte de Pontchartrain.
Legacy.
Lake Pontchartrain in Louisiana was named after him, as well as the historic Hotel Pontchartrain in New Orleans. 
In Michigan his name was given to Fort Pontchartrain du Détroit (the site of modern-day Detroit), and to Detroit's Hotel Pontchartrain.
Isle Phelipeaux, Isle Pontchartrain, and Isle Maurepas, which appear on early maps of Lake Superior, were named in his honor by Pierre François Xavier