Major, U.S. Army, 306th Infantry, France, 1917; Partner, Schultze and Weaver, Architects, New York, NY, 1921-1939;

B.S. Engineering, University of Pennsylvania, Philadelphia, PA, 1902;

Weaver was raised in Philadelphia, PA, and attended college there. He traveled widely and resettled in New York City by the 1910s. Aside from business travel, he lived here for his whole life; for a long period, he owned an apartment at 299 Park Avenue and a country estate, Spencecliff, in East Hampton, Long Island, NY.

His parents were James Buchanan Weaver of Fairfax Court House, VA, and Mary Fullerton Weaver of Philadelphia, PA; he was a great-great-grand nephew of President James Buchanan. He had a sister, Mrs. James M. Repplier.

Weaver was married twice, the first time to Emily Stokes Weaver of Philadelphia, PA, (d. 10/14/1930) with whom he had three children and from whom he was divorced before 1929. He and Emily had tennis in common; she won two national indoor tennis doubles championships in 1914 and 1918; in 1920, he became President of the West Side Tennis Club. In 1929, he married Lillian Leacock Howell Weaver (d. 01/23/1959).

He had a daughter, Lillian H. Weaver, and two sons, S. Fullerton Weaver, Jr., and Clifton S. Weaver.

Known as Major Weaver, he was trained as a civil engineer, and during the 1910s he developed Park Avenue apartment buildings on land leased from the New York Central Railroad near Grand Central Station. Notable among these were the 400 Park Avenue Building (1914-1915) and the 420-430 Park Avenue Apartments (1916). He built up enough wealth to buy the Park Lane Apartment Hotel. Weaver's high-profile development activities enabled him to become a member of the New York Real Estate Board of Governors. His partnership with Leonard Schultze occurred after his solo career in real estate, during which he had made many social connections on the Eastern Seaboard, relationships that would build the Schultze and Weaver client list. Other connections came from the many social, sport and country clubs to which belonged, including the Westide Tennis Club, University of Pennsylvania, the Lotus, Oakland Golf, Maidstone, and Turf and Field Clubs. (In 1929, he also belonged to Midwick Club of Pasadena, CA, and the elite Jonathan Club of Los Angeles, CA.) After World War I, he was also active in veterans' groups, particularly the Military Order of Naval and Army Officers of the World War, of which he was a Governor.