Dr. William Newton Mercer

William Newton Mercer (1790 – August 16, 1874) was a surgeon, plantation and slave owner in the lower Mississippi River valley before the American Civil War, banker, and civic leader of 19th-century New Orleans. His New Orleans residence later became the clubhouse of The Boston Club, which has been associated with the history of business and Carnival in New Orleans.

Early life William was born in 1791 in Cecil County, Maryland. His parents were Anna and Benjamin James Mercer. He studied medicine at the University of Pennsylvania School of Medicine under Benjamin Rush. Mercer owned 342 slaves, and was the 12th-largest slave owner in the state. Mercer also owned property in Illinois (roughly half of Macoupin County) and Louisiana.

He served as president of the Bank of Louisiana, and trustee at Natchez Academy. He was a member of Christ Church Cathedral and president of St. Anna's Asylum in New Orleans.

Politically, Mercer was a Whig until the collapse of the party in the 1850s. Henry Clay stayed at Mercer's house when he visited New Orleans in 1851. Following the American Civil War, he resided in New Orleans and was a "major aide to Henry C. Warmoth—the 'carpetbag' governor" during the Reconstruction era. When he died in New Orleans at age 83, his estate was valued at .

Associations Mercer was a member of the Union Club of New York starting in 1852. Along with Duncan and planter Levin Marshall, Mercer stood apart from planters like the Kers, the Nutts, the Liddells, and the McGehees in that they socialized far beyond New Orleans, and thus "attained the wealth, connections to the outside, and acquisitive instincts to give their entrepreneurial drive full scope".

A Louisianan recalled in 1967 that as of the 1940s there were stacks of letters between Mercer and Henry Clay, Daniel Webster, and James K. Polk in the library at Laurel Hill mansion at White Cliffs.

Personal life In 1823, Mercer married in Natchez, Ann Eliza Farar. Farar was the daughter of Benjamin Farar and Mary Ellis, heiress of Richard Ellis, the original recipient of the Spanish land grant of , including Ellis Cliffs, Mississippi, and Laurel Hill Plantation in Adams County, Mississippi. The family resided at their Laurel Hill Plantation in Adams County, where Mercer built St. Mary's Episcopal Chapel. Ann Eliza Farar Mercer suffered from a "protracted illness" in the 1830s and the family traveled to Europe in search of treatment options. His wife died of consumption in November 1839. Their daughter died not long after. Mercer, his wife, and his daughter are all buried together in Natchez. It fell out of regular use by 1850. Church services had been segregated by race.