Alexander Slidell Mackenzie (1803–1849) Born in New York City, Mackenzie was a U.S. Navy officer who served during the first half of the 19th century. He was an accomplished author and writer who wrote several contemporary essays and biographies of notable US naval figures of the early 19th century. He was the brother of U.S. Senator John Slidell of Louisiana, who was later involved in the American Civil War's "Trent Affair."