William Henry Barnum was a real estate developer in New York City. According to a descendant, Larry McCagg, he virtually invented mortgage banking in New York in the 1920s. Needless to say, most was lost in the Depression, but the tradition lingers on.
From the New York Times of April 30, 1963: (died 4/26/1963): William Henry Barnum, president of the Park and 46th Street Corporation, owners of the Postum Building at 250 Park Avenue, died Friday in his home at 150 East 73 Street. He was 81 years old. Mr. Barnum was graduated in 1904 from the Sheffield Scientific School of Yale University. He was head of an investment firm, William Henry Barnum & Co., Inc. in 1929 when with a group of bankers and real estate men he organized the Continental Mortgage Guarantee Company. For a number of years he was president of Continental, which operated in the first mortgage field. In 1939, Mr. Barnum negotiated the 26 year lease renewal of the General Foods Corporation at 250 Park Avenue for 110,000 square feet of space at an aggregate value of $7,000,000. It was termed one of the largest lease renewal contracts of the period. In World War I, Mr. Barnum was appointed chairman of the City Advisory Committee of the War Camp Community Fund by Secretary of War Newton D. Baker. During the 1940s, Mr. Barnum was also president of the Continental Realty Investing Company which owned or controlled several important city buildings. He belonged to the Links Club. He leaves two daughters, Mrs. Edward K. McCagg and Miss Harriet Barnum; two brothers, Walter B. and Phelps; one sister, Mrs. Laura Levering and three grandchildren.