In 1840 Thomas Carling began a small brewing operation in London, Ontario selling beer to soldiers at the local military camp. When he died, his sons William and John took over, naming it the W & J Carling Brewing Co. John Carling became a prominent figure in Canadian business and politics and was later knighted in 1893. Sir John Carling died in 1911. The Carling operation then changed hands several times. In 1930 the Carling company was sold to Canadian Breweries Limited, founded by E.P. Taylor.
Eugene O'Keefe, a wealthy banker, purchased the Hannath & Hart Brewery in 1862. By 1864, one of his partners had died, while the other Patrick Cosgrave left to found his own brewery. The business was renamed O'Keefe and Company. It was the first to produce lager beer in Canada along with the traditional ale and porter.  In 1891 the company was incorporated as O'Keefe Brewing Company Limited. In 1911 another new brewery was built with an annual capacity of 500,000 barrels a year.  O'Keefe was one of the first to use trucks for beer delivery, the first to build a mechanically refrigerated warehouse, and one of the first to advertise extensively. 
Canadian Breweries 1930-1969
Carling was acquired in 1930, and O'Keefe by 1934. Canadian Breweries Limited was a conglomerate, having purchased about 30 breweries. Some of the original brand names stayed in use during this time.
Canadian Breweries was sold to Rothmans 1969 and resulted in a new brewer called Carling O'Keefe in 1973.
Carling O'Keefe 1969-1989
Carling O'Keefe was bought by Elders IXL of Australia in 1987 and later merged with Molson to form Molson Breweries Canada in 1989. At the time of the merger, Molson was the second largest Canadian brewing company, while Carling O'Keefe was third. The merger put the combined company ahead of former market leader Labatt, and made it the sixth largest North America brewery. Seven Canadian plants were closed due to consolidation. 
Port Carling, Ontario is named for John Carling.
Carling sponsored Orteig Prize contenders Capt. Terry Tully, and Lieut. James Medcalf in their plane the Sir John Carling. They took off on August 28, 1927 from London, Ontario, headed for London, England (United Kingdom), but they never returned.
From 1993 to 2001 Carling was the sponsor of the FA Premier League, one of the top sporting leagues in the world, as well as Celtic Football Club and Rangers Football Club, the two largest Scottish teams. Carling owned the Quebec Nordiques of the World Hockey Association in the 1970s. Carling is also known for sponsoring various live music venues in the United Kingdom, including Carling Academies in Brixton, Glasgow, Birmingham, Bristol, Islington, Liverpool and Newcastle upon Tyne; the Shepherd's Bush Empire; the Manchester Apollo and the Carling weekend music festivals which takes place at the end of August each year over two venues- Leeds and Reading.
Carling O'Keefe was a major supporter of Langley Speedway, a 3/8th mile paved stock car oval, in Langley, British Columbia. They often sponsored races and season points championships. For example, Tom Berrow was the 1976 Carling O'Keefe Super Stock Points Champion. Their Company name was painted on the front stretch of the track and was part of the "Winner's Circle" celebration. Carling O'Keefe also held ownership of the NHL's Quebec Nordiques and the CFL's Toronto Argonauts, before selling the franchises in 1988 due to the impending merger with Molson. The company, however, maintained promotional interests in both teams.
- Carling Black Label is the best selling beer in the United Kingdom. The "Mabel, Black Label" was a well-known advertising slogan
- Carling Premier a stronger version of Carling Black Label, with an alcohol percentage of 4.7%. In cans it is sold with a widget.
- Red Cap Ale - now produced by Brick Brewing
- Old Vienna
- Molson merges with Carling - CBC News: National, Broadcast Date: Jan. 18, 1989; reporter Tom Kennedy
- Falstaff Brewing — History of Carling
- University of Western Ontario - Partial essay on the History of Carling
- Museum London — Carling
- Glenbow Museum — The Molson Papers