Born in Los Angeles, California, Rees was educated in local public schools. B.A., Occidental College, Los Angeles, California, 1950. He attended University of California Law School, 1951. He was in the United States Army. He was a lawyer in private practice. He served as president of Compania del Pacifico, a Latin American export firm. He served as member of the California state assembly from 1954 to 1962. He served as member of the California Senate from 1962 to 1965. He served as delegate, Democratic National Conventions, 1956, 1960, 1964, and 1968.
Rees was elected as a Democrat to the Eighty-ninth Congress, by special election, to fill the vacancy caused by the resignation of United States Representative James Roosevelt, and reelected to the five succeeding Congresses (December 15, 1965-January 3, 1977). He was not a candidate for reelection to the Ninety-fifth Congress in 1976. He served as president, Community Development and Management, San Jose, California. He died on December 9, 2003, in Santa Cruz, California.