Clarence Mackay was the son of Dublin-born John Mackay who arrived in New York in 1840 and relocated to Nevada, where he made his fortune after discovering an enormous silver deposit. Thereafter, Mackay went into the undersea cable business and became a communications titan. At his death in 1902, his son Clarence was left chief of the Postal Telegraph Corp. After John gave his son Clarence the 600 acre Harbor Hill estate in Roslyn upon his marriage in 1898, Clarence contracted Stamford White as architect for his mansion. He held various large parties at Harbor Hill, including for the Prince of Wales in 1924 and for Charles Lindbergh in 1927. In 1928 he sold the holdings in his companies to IT&T but suffered devastating losses during the depression, forcing him to close the main house and move to the superintendent's house. He died in his New York residence at 75th Street in 1938.