In a second career begun in his retirement, Henry Morrison Flagler (1830–1913), the cofounder of Standard Oil and one of the wealthiest citizens in the United States, embarked on the development of the tropical wilderness of Florida. Starting in St Augustine, he built a network of luxury hotels and railroads that became the infrastructure for modern Florida. Creating a counterpart to the premier summer resort of Newport, Rhode Island, Flagler transformed Palm Beach, an undeveloped barrier island, into a winter playground for the new American aristocracy, starting with the Georgian-style Royal Poinciana Hotel. It was Whitehall, however, the mansion built for Flagler in 1900–02 as a wedding gift to his third wife, Mary Lily Kenan, that became the resort community’s monumental showplace. Designed by the New York firm of Carrère & Hastings in the Renaissance-derived classicism of the World’s Columbian Exposition of 1893, the stately white palace fronting Lake Worth embodied Flagler’s cultural aspirations as a patron of the arts. As the first major client of Carrère & Hastings, Flagler was critical in launching the career of one of the most prominent architectural firms of the Gilded Age. This article examines Whitehall in the context of Flagler’s business practices and personal goals, consistent with Andrew Carnegie’s ‘Gospel of Wealth’. Architectural opulence not only boosted Flagler’s mercantile purposes, but also reflected a belief, nurtured by his relationship with Carrère & Hastings and other close associates, about the importance of classical architecture and the arts in the development of society.