He found employment with the Washington State Tax Commission as an auditor; he was soon promoted to become the organization's director of research.
He left government in 1961 to serve as vice president of Continental Illinois Bank with former colleague David M. Kennedy, who worked with him in the Department of Treasury.
[1][3] Known for his detail orientation and conservative views on spending from his time in Washington, Mayo was chosen in 1969 by incoming President Richard Nixon to develop his initial policy budgets; Mayo was considered to be a proponent of Nixon's black capitalism programs, which were designed to boost the economic fortunes of African Americans through loans and investment in black-owned business.
At the meeting, Mayo made the mistake of complaining that John Ehrlichman, who was Nixon's chief domestic adviser, was ostensibly intruding on his turf and threatened to resign if his relations with the president didn't improve, leading Nixon to conclude "I guess Mayo has got to go.
"[5] In July 1970, Nixon appointed Mayo as head of the Federal Reserve Bank of Chicago, which allowed him to return to his adopted hometown.