Rockwood Hall was a Gilded Age mansion in Mount Pleasant, New York, on the Hudson River. It was best known as the home of William Rockefeller, brother of John D. Rockefeller. Both brothers were co-founders of the Standard Oil Company. Other owners of the house or property included Alexander Slidell MacKenzie, William Henry Aspinwall, and Lloyd Aspinwall. The property was once up to 1,000 acres (400 ha) in size; the mansion at its height had 204 rooms, making it the second-largest private house in the U.S. at the time, only behind the Biltmore mansion in North Carolina. The estate is currently an 88-acre (36 ha) section of the Rockefeller State Park Preserve.

William Avery Rockefeller Jr. was an American businessman and financier. Rockefeller was a co-founder of Standard Oil along with his elder brother John Davison Rockefeller. He was also a part owner of Anaconda Copper, which was the fourth-largest company in the world by the late 1920s. Rockefeller started his business career as a clerk at 16. In 1867, he joined his brother's company, Rockefeller, Andrews & Flagler, which later became Standard Oil. The company was eventually split up by the Supreme Court in 1911. Rockefeller also had a significant involvement in the copper industry. In 1899, Rockefeller and Standard Oil principal Henry H. Rogers joined with Anaconda Company founder Marcus Daly to create the Amalgamated Copper Mining Company, which later returned to the name Anaconda Copper.