Flagler, Henry Morrison, 1830–1913, American financier and real-estate developer, b. Hopewell, near Canandaigua, N.Y. As a youth he struck out for himself in Ohio. After trying the grain and salt business, he joined John D. Rockefeller in oil refining. The firm of Rockefeller, Andrews & Flagler became the Standard Oil Company in 1870, and Flagler was connected with it until 1911, resigning as vice president, however, in 1908. He had been Rockefeller's closest associate in the early development of the company.
Flagler visited Florida in 1883, and, annoyed at the inadequate transportation and hotel facilities, he undertook to improve them. He bought up and consolidated several local railroads and organized the Florida East Coast Railway, which he extended S from Daytona through Palm Beach (1894) to Miami (1896) and thence 150 mi (241 km) to Key West (1912). He established steamship lines, dredged the Miami harbor, and built palatial hotels, all to encourage the development of Florida as a winter playground. He also made anonymous gifts to build schools, churches, and hospitals. Altogether Flagler invested over $40 million in the peninsula and, more than any other, was responsible for Florida's growth.
See S. W. Martin, Florida's Flagler (1949).