In 1945, with his brother Joseph (Jack), Harrison founded his own semi-pro team, the Rochester Pros; in 1946, the franchise changed its name to Royals and began play in the National Basketball League (NBL).
King received taunts from crowds at times, particularly in the playoff series on the road in Fort Wayne, Indiana.
Owing to a variety of circumstances (Harrison had stated the team's need for a guard to go with Maurice Stokes), the Royals drafted Si Green over Bill Russell, who was selected by the St. Louis Hawks before being traded to the Boston Celtics for Ed Macauley and Cliff Hagan.
I thought even from the start that one day it would become big, real big, and it has.” Harrison coached many Naismith Basketball Hall of Famers, including Bob Davies, Red Holzman, Bobby Wanzer, Al Cervi, Arnie Risen, Pop Gates and Alex Hannum.
He also coached Pro Football Hall of Fame quarterback Otto Graham, Chuck "The Rifleman" Connors and Del Rice, an MLB player and the manager of the California Angels in 1972.
In light of having no wife or children (as was the case with his brother and sister) to leave his belongings to, he bequeathed his Hall of Fame ring, jacket, and artifacts to David and Wendy Dworkin (her mother Barabara was the cousin of Harrison).
For his part, Harrison in his later years stated the importance of Syracuse owner Danny Biasone (inducted into the Hall of Fame after his death in 2000) in getting the "fans' interest" with the shot clock that he was responsible for lobbying for the NBA to adopt in 1954; Harrison put his full support behind the idea done by Biasone along with Leo Ferris, which still is in use today.