Holohan was born in Watsonville, California to Richard and Catherine Lynch Holohah, both immigrants from Ireland.

[1] Four years later, in 1908, he ran for California State Senate for the 29th district, defeating fellow Democrat Hall C. Ross with a plurality of the vote.

[4][5] He retired after his first term to be appointed as United States Marshal of the Northern District of California on January 13, 1914, by President Woodrow Wilson.

[10] In 1924, he retired as marshal and was appointed as Sheriff of Santa Cruz County a year later, winning a full term in 1926.

On September 1, 1927, Governor C. C. Young appointed Holohan as the warden of the San Quentin State Prison, later being re-appointed by James Rolph.