The IBL was founded in 1919 with just four teams—Galt, Guelph, Stratford and Kitchener—and is believed to be the oldest amateur men's league in Canada and also one of the best, regarding quality of play. During the early years, the league expanded to include the cities of London, Brantford, Preston and St. Thomas, Ontario.
The league's first commissioner in the 1950s was John Gillies, a London, Ontario, lawyer and former pitcher in the league for the London Majors.
It was previously known as the Intercounty Major Baseball League and the Senior Intercounty Baseball League. The teams play for the Jack and Lynne Dominico Trophy, which is awarded to the league champions. Jack and (and the late Lynne) Dominico own the Toronto Maple Leafs Baseball Club.
The is the only Amateur that I will cover
1919 Galt, Guelph, Stratford and Kitchener
1920 to 1952 Unknown Teams
1954 Brantford, Galt, Guelph-Waterloo, Kitchener, London, St Thomas
1955 to 2000 unknown
2001 Barrie, Brantofrd, Guelph, Hamilton, Kitchener, London, St Thomas, Toronto, Waterloo
2002 Oshawa enter the league
2003 Stratford enter the league and St Thomas and Waterloo has left the league
2005 to 2008 No Teams enter or left the league
2009 Mississauga enter the league an Stratford has left the league
2010 Ottawa enter the league and Oshawa has left the league.
2011 Burlington enter the league and Guelph and Mississauga left the league
2012 Guelph enter the league.
2013 Ottawa has left the league.
2014 No Teams enter or left the league
2015 No Teams enter or left the league
2016 No Teams enter or left the league
2017 No Teams enter or left the league