In Washington, D.C., Delano was the architect for the 1927 renovation to the White House, which later led to structural problems and rebuilding during the Truman Administration. ("See" White House Reconstruction.) He served on the National Capital Planning Commission and the U.S. Commission of Fine Arts from 1924 to 1928, including a term as vice chairman in 1928. This service led to his firm receiving the design contract for the New Post Office building, completed in 1934, in the Federal Triangle complex. Delano served on the board of design for the 1939 New York World's Fair and consulted on the controversial White House Truman Balcony in 1946, prior to the reconstruction project of 1949–52.