Captain Mayo commanded Mare Island Naval Shipyard in 1903, before becoming the aide for the Secretary of the Navy Josephus Daniels.

[2] About 1909 he was in command of the cruiser USS Albany as she cruised in Central American waters protecting United States citizens and interests as part of the Special Service Squadron.

Appointed rear admiral in 1913, he commanded the naval squadron involved in the Tampico incident of 9 April 1914.

Naval Forces both in American and European waters, he was awarded the Navy Distinguished Service Medal and various foreign decorations.

Admiral Mayo retired 28 February 1921, and, for four years, served as Governor of the Philadelphia Naval Home.