Whitman Blount Mayo was born in New York City and grew up in Harlem and Queens. At the age of 17, he moved with his family to Southern California and from there entered the United States Army, serving from 1951 to 1953 during the Korean War. Upon release, he studied at Chaffey College, Los Angeles City College, and UCLA. During this time, he began acting in small parts, while waiting tables and working in the vineyards and as a probation officer, as well as a variety of other small jobs. He also spent seven years as a counselor to delinquent boys.
Also in the late 1970s, Mayo appeared on the Los Angeles children's television program That's Cat, offering sage advice in a sweet manner to the main character, Alice.
Mayo later starred in Grady, an unsuccessful spin-off in which his character moved in with his daughter and her husband in Beverly Hills. After its cancellation in 1976, Mayo's Grady character returned to Sanford and Son.
Mayo reprised the role in the unsuccessful 1977 NBC-TV spinoff series Sanford Arms opposite actor Theodore Wilson, and for two episodes of Sanford, another NBC-TV Sanford and Son spinoff, this time opposite Redd Foxx and actor Dennis Burkley, in 1981.
In 1990, he appeared in an episode of In The Heat of the Night titled "Hello in There".
In 1991, he appeared in an episode of Full House titled "The Volunteer". He played a senior named Eddie Johnson with Alzheimer's.
In 1996, Late Night with Conan O'Brien spent several weeks trying to have Mayo appear on the show. Conan even went as far to set up the "Grady Hotline", a 1–800 number where viewers could call in with any Grady "sightings". The show also aired a mock episode of Unsolved Mysteries. On February 8, 1996, Mayo appeared on Late Night, to much fanfare. In 1997, he guest-starred in the Nickelodeon sitcom Kenan and Kel, playing Kenan and Kyra's rude, impatient Uncle Raymond.
Mayo died of a Heart failure on May 22, 2001 at Atlanta's Grady Memorial Hospital. He had resided in Atlanta's Collier Heights community since 1994 and was survived by his third wife, Gail Mayo. His son, Rahn Mayo, became a member of the Georgia House of Representatives in 2009.
