The first Professional Football League in America that openly paid its players was the Ohio League (1902-1919). Four of its leading teams, including the Canton Bulldogs asked teams in Pennsylvania and New York State to form a National League in 1920 – thus the NFL was born.
Semi-Pro Leagues exist all over USA, organised roughly on state lines.
Below you will find a link to Irish Connections throughout the USA
New York Metropolitan Area:
Cal-exico (California-Mexico Leagues):