Walter Mayo Macomber apprenticed at the Boston Architectural Club and with his father, who was an architect, cabinetmaker, and builder. He served in the French ambulance corps during World War I prior to joining the Boston architecture firm Perry, Shaw & Hepburn. In 1928 he became the resident architect at Colonial Williamsburg, supervising its restoration and reconstruction until 1934; he then became the resident architect at Mount Vernon for thirty years. He formed an architectural practice in Washington, D.C., in 1958 with Walter Peter Jr. and after 1964 practiced in his own firm. He designed numerous restoration projects for historic properties, including Stratford Hall, President Monroe's law library, and the Fairfax County Court House; he completed the installation of the historicist diplomatic reception rooms at the Department of State in 1985 at age ninety.