John Slidell (slīdĕl´, slī´dəl), 1793–1871, American political leader and diplomat, b. New York City. He became a prominent lawyer and political figure in New Orleans and served as a Democrat in Congress (1843–45). In 1845, Slidell was appointed special U.S. envoy to Mexico to adjust the Texas boundary and to negotiate the purchase of California and New Mexico; the Mexican government, which had broken off diplomatic relations after the U.S. Congress had provided for the annexation of Texas, refused to receive him (see Mexican War). Senator from Louisiana (1853–61), he was influential in securing the nomination and election of James Buchanan to the presidency (1856) and was a power in the administration. Slidell joined the Confederate cause early in 1861. Appointed Confederate commissioner to France the same year, he figured with James M. Mason in the Trent Affair. Although cordially received in Paris, Slidell was unable to get official recognition or any material aid for the Confederacy from the French emperor, Napoleon III. After the Civil War, Slidell resided in France.
See L. M. Sears, John Slidell (1925); B. Willson, John Slidell and the Confederates in Paris (1932, repr. 1970).