He moved to the World Wide Wrestling Federation in the early seventies and became the villain Blackjack Mulligan. At first Mulligan, donning black trunks, black hat, black glove, and using the iron claw submission hold. He received a push and went on to wrestle Pedro Morales and Bruno Sammartino.
He then started teaming with Blackjack Lanza and formed The Blackjacks, who won the WWWF World Tag Team Championship in August 1975.
In 1986, Mulligan wrestled under a mask as "Big Machine," part of a team with "The Giant Machine" (André the Giant) and "Super Machine" (Demolition Ax) collectively known as The Machines.
Mulligan and his Blackjacks partner, Jack Lanza were inducted into the WWE Hall of Fame on April 1, 2006 by their manager, Bobby Heenan.
On April 7, 2016, Mulligan passed away.