Note: Numbers after some Chapter names indicate sequence when more than one Chapter has existed at that location.
| 1944 | Windsor Chapter launched as Ontario’s first. |
| 1945 | New Chapters: Chatham (1), London, Sarnia, Toronto, with Society’s first University Chapter, University Chapter at Assumption College, Windsor. |
| 1946 | New Chapters: Grand Valley, Kitchener-Waterloo, Orillia (1), Wallaceburg (1). Ontario District founded Oct. 19, 1946, at The Grigg Hotel, London. |
| 1947 | New Chapters: Amherstburg, Brantford (1), Hamilton (1), Stratford (1). |
| 1948 | New Chapters: Guelph (1), Paris, Sudbury (1). |
| 1949 | New Chapters: Kenora, Kingston (1), Oshawa, Peterborough (1). |
| 1950 | New Chapters: Belleville, East York, Hagersville, Leamington, Metro (1), Niagara Falls (1). |
| 1951 | New Chapter: St. Catharines. Toronto Chapter hosts Midwinter Convention – first time held outside USA. |
| 1952 | New Chapters: Bracebridge, Midland (1), Orillia (2), Yorktown. “The Four Chorders” place 2nd at International Convention – highest placing ever by an Ontario quartet to that point, and still tied for the highest ever. |
| 1953 | New Chapter: Woodstock. |
| 1954 | New Chapters: Scarborough, Welland. |
| 1956 | New Chapters: Aurora, Barrie (1), Simcoe. |
| 1957 | New Chapters: Burlington, Brockville (l), Ottawa, Port Hope, Cobourg (1), St. Catharines. |
| 1958 | New Chapters: Oakville (1). For the first time, Ontario sends no chorus to International Contest |
| 1959 | New Chapters: Brampton (1), Kingston (2), Motor City. |
| 1960 | New Chapters: Cornwall (1), Etobicoke, Metro (2), Wallaceburg (2). APOC (“Association of Past Ontario District Quartet Champions”) formed. |
| 1961 | New Chapter: Chatham (2). |
| 1962 | New Chapters: Amherstburg (2), Stratford (2), Walkerton. |
| 1963 | New Chapters: Hamilton (2), North Bay (1), Owen Sound, North York. First International Convention held in Canada (Toronto). “Nighthawks” quartet places close second |
| 1964 | New Chapters: Georgetown, Huronia, Listowel, Smiths Falls, Wingham. |
| 1965 | New Chapter: Lindsay (1). |
| 1966 | Harmony Hall opens in East York, & Ontario becomes first District to have a permanent headquarters. |
| 1967 | New Chapters: Fort Erie, Peterborough (2). |
| 1968 | New Chapters: Grimsby, Guelph (2), Hanover, Markham, Oakville (2), St. Thomas. |
| 1969 | New Chapter: Niagara Falls (2). |
| 1970 | New Chapters: Brampton (2), Mount Forest. |
| 1971 | New Chapter: Thornhill. |
| 1972 | Scarborough chorus changes name to “The Dukes of Harmony” and makes top ten at International. |
| 1973 | New Chapters: Thunder Bay, Trenton. Harmony Ranch established, near Sutton on Lake Simcoe. |
| 1974 | New Chapters: Brockville (2), Dunnville. |
| 1975 | New Chapter: Midland (2). |
| 1976 | New Chapters: Barrie (2), Mississauga, Port Hope (2). |
| 1977 | New Chapter: Uxbridge. Scarborough’s “The Dukes of Harmony” become first-ever Canadian International Chorus Champs. Ontario District establishes “Harmonize for Speech”, its own unified charitable fund. (First District to take such an action.) |
| 1980 | “The Dukes” win again as International Champs. A consecutive win, by Contest rules. |
| 1981 | New Chapter: Stoney Creek. |
| 1982 | New Chapter: Cataraqui. |
| 1983 | New Chapters: Collingwood, Seaforth. |
| 1984 | Ontario “Trillium” chorus visits BABS (“British Association of Barbershop Singers”) Convention in England. |
| 1985 | New Chapters: Lindsay (2), Orangeville. |
| 1987 | George Shields, H4S founder, awarded The Order of Canada. |
| 1988 | Harmony Woods established, near Parkhill. |
| 1989 | New Chapter: North Bay (2). Barbershoppers put on show at first International choral festival, “The Joy of Singing”, Roy Thompson Hall, Toronto. |
| 1990 | New Chapter: Huntsville. Tri-City Chorus tours Jamaica. Ontario reaches first $1,000,000 raised for H4S. Sarnia Chapter celebrates 50th anniversary. |
| 1993 | New Chapters: Brockville (3), Newmarket. |
| 1994 | New Chapter: Sudbury (licence). District membership reaches 1700. Ontario COTS used as model for Society revitalization program. |
| 1995 | New Chapters: Brantford (lic), Cornwall (2), Strathroy. Ontarian Randy Chisolm is first Canadian to win a Quartet Gold Medal. London Chapter celebrates 50th anniversary. |
| 1996 | Ontario District and Kitchener- Waterloo-Chapter celebrate 50th anniversaries. |
| 1998 | Renamed Chapters: Cataraqui to Kingston, Trenton to Quinte Regional. New Chapters: Greater Toronto, Toronto (2). |
| 1999 | H4S reaches $2,000,000. Society Board meets at Ontario District Spring Convention – first time for such a meeting outside Kenosha. TNL placed 11th at International. |
| 2000 | New Chapters: Nepean (2). East York Chapter celebrates 50th anniversary. TNL placed 5th at International |
| 2001 | St. Catharines Chapter celebrates 50th anniversary. TNL placed 2nd at International. |
| 2002 | TNL placed 2nd at International. |
| 2003 | TNL and MegaCity both go to International- an Ontario first. Orangeville chapter returns licence and several members move to Mount Forest, Simcoe, or Barrie. |
| 2004 | London celebrates 60th anniversary. TNL placed 2nd at International. |
| 2005 | Hamilton chapter created following the disbanding of Stoney Creek chapter. Sarnia celebrated its 60thanniversary. TNL and MegaCity go to International again. Burlington chapter becomes a seniors afternoon group |
| 2006 | K/W Chapter celebrates 60th anniversary |
| 2007 | Oshawa celebrates 60th anniversary. Ottawa qualifies to go to International. |
| 2008 | George Shields inducted into the BHS Hall of Fame |
| 2012 | New Chapter: Middlesex Centre |
| 2013 | TNL wins International Chorus gold, Border Patrol wins International Seniors Quartet gold. Greg Backwell inducted into the BHS Hall of Fame |
| 2015 | New Chapter: Northumberland Hills |
| 2018 | Dr. Ray Danley inducted into the BHS Hall of Fame |
| 2019 | DoubleDouble wins International Seniors Quartet gold |
| 2023 | Maple Reserve earns the spot as 11th place mic testers for International Quartet Finals, the highest placing for an Ontario quartet in 55 years. |
| 2024 | Steve Armstrong inducted into the BHS Hall of Fame |