He engaged in the banking business with American Trust Co., San Francisco, Calif., in 1940 and 1941. He served as assistant naval attaché in the United States Embassy in London in 1939 and 1940; with Bureau of Naval Personnel, Washington, D.C., in 1941 and 1942; attended the
Naval War College in 1942; was assigned to duty on staff of Seventh Amphibious Force as flag lieutenant and aide to Vice Adm. D.E. Barbey in 1943 and released to inactive duty in March 1946 as a
lieutenant commander; He was a permanent Representative of the United States to the
Organization of American States with the rank of ambassador, March 7, 1974, to February 1, 1977, and nominated by President
Gerald R. Ford and confirmed by the
United States Senate on December 10, 1975, to be a member of the Board of Directors of the Inter-American Foundation and was a resident of the community of
Belvedere, California, consisting of the eponymous island, along with part of
Corinthian Island, in the
San Francisco Bay, just offshore from the
Tiburon Peninsula. He moved to
San Francisco, California, before his death. Mailliard voted in favor of the
1957 Civil Rights Act, the
Civil Rights Act of 1960, the
Civil Rights Act of 1964, and the
Civil Rights Act of 1968. He voted as well for the
24th Amendment to the U.S. Constitution and the
Voting Rights Act of 1965. ==Personal life==