city, seat (1884) of Jefferson parish, southeastern Louisiana, U.S. It lies along the west bank of the Mississippi River (there bridged) opposite New Orleans. Founded in the early 1800s as Mechanicsham by Nicholas Noel Destréhan, a plantation owner, it was settled by immigrants of German descent. Gretna was renamed in the 1880s for Gretna Green, Scotland, because of its reputation for quick weddings (which are still performed there). In 1913 Gretna merged with nearby McDonoghville to form an incorporated city. Once a shipping point for plantations, truck farms, and dairies, it has developed as a residential-industrial suburb of New Orleans. The city's primary manufactures are cottonseed oil and petroleum products. Pop. (1990) 17,208; (2000) 17,423.