Question: The Happy Meal was invented by the restaurant chain founded in what year?

Context paragraphs:
Zambrero: Zambrero is an Australian restaurant chain serving Mexican food.  It was founded in 2005 in Canberra by then-medical student Sam Prince with the idea of using the profits to support humanitarian causes.  The chain donates a meal to someone in need in the developing world for every meal purchased through their Plate4Plate program.

Clock (restaurant): Clock was a Swedish hamburger restaurant chain founded by an offshoot from the US-based Carrols.  The chain suffered from mismanagement and declared bankruptcy; as the government had acquired the forfeited company, it was incorporated into the state-owned restaurant chain SARA.

McDonaldland: McDonaldland was a fantasy world used in the marketing for McDonald's restaurants.  McDonaldland was inhabited by Ronald McDonald and other characters.  In addition to being used in advertising, the characters were used as the basis for equipment in the playgrounds attached to some McDonald's.  McDonaldland and the supporting characters were dropped from McDonald's marketing in 2003, but Ronald McDonald is still seen in commercials and in Happy Meal toys.

McDonald's: McDonald's is an American hamburger and fast food restaurant chain.  It was founded in 1940 as a barbecue restaurant operated by Richard and Maurice McDonald, in San Bernardino, California.  In 1948, they reorganized their business as a hamburger stand, using production line principles.  The first McDonald's franchise using the arches logo opened in Phoenix, Arizona in 1953.  Businessman Ray Kroc joined the company as a franchise agent in 1955 and subsequently purchased the chain from the McDonald brothers.  Based in Oak Brook, Illinois, McDonald's confirmed plans to move its global headquarters to Chicago by early 2018.

P. F. Chang's China Bistro: P. F. Chang's China Bistro is an Asian-themed US casual dining restaurant chain founded in 1993 by Paul Fleming and Philip Chiang, owned and operated by Centerbridge Partners, and headquartered in Scottsdale, Arizona.  As of October 2014, P. F. Chang's operated 204 restaurants in the United States and 56 in international markets under licensee agreements.  Countries include Canada, Puerto Rico, Mexico, Argentina, Chile, Brazil, Colombia, Costa Rica, Panama, Turkey, Lebanon, Philippines, South Korea, Dominican Republic, Egypt, Jordan, Kuwait, Qatar, Saudi Arabia and United Arab Emirates.  It is the largest full service casual dining Chinese restaurant chain in the United States, with locations across the country.

Happy Meal: A "Happy Meal" is a form of kids' meal sold at the fast-food chain McDonald's since June 1979.  A toy is included with the food, both of which are usually contained in a box or paper bag with the McDonald's logo.  The packaging and toy are frequently part of a marketing tie-in to an existing television show, film, or toy brand.

Red Barn (restaurant): The Red Barn restaurant was a fast-food restaurant chain founded in 1961 in Springfield, Ohio, by Don Six, Martin Levine, and Jim Kirsch.  In 1963, the small chain was purchased by Richard O. Kearns, and the offices moved briefly to Dayton, Ohio, followed by a move in August 1964 to Fort Lauderdale, Florida.  In the late 1960s, Servomation bought the company.  The new parent company itself was bought by Motel 6 in the late 1970s.  Only interested in the core business of Servomation, the new owners ceased advertising for the chain and the franchise leases were allowed to expire, with the last of the leases expiring around 1988.  At its peak, Red Barn had 300-400 restaurants in 19 states, as well as outlets in southern Ontario, elsewhere in Canada, and Australia.

Bennigan's: Bennigan's is an Irish pub-themed casual dining restaurant chain founded in 1976 in Atlanta by restaurateur Norman E. Brinker as one of America's original casual dining concepts.  The chain operated under the restaurant division of Pillsbury for most of its history, until Pillsbury was bought out by the British liquor conglomerate Grand Metropolitan Known.  Due to laws preventing liquor manufacturers from also operating liquor sellers, the chain was sold to Texas-based Metromedia restaurants, until the company filed for bankruptcy in 2008.  The chain then went through a series of restructuring and ownership changes until it was purchased by Legendary Restaurant Brands, LLC in 2015.  The company is now operating out of Dallas, Texas.

Good Earth (restaurant chain): Good Earth was a health food restaurant chain founded in Reno, Nevada and one in San Rafael, California owned by Dean Stanley Ashby and family wife Georgia Anne Ashby Aaron Stanley Ashby and the youngest Dean Stanley Ashby II by William A. Galt that existed in the US in the 1970s.  It was purchased by General Mills in 1980, which converted most of the restaurants into other chain restaurants they were operating, such as Red Lobster and Olive Garden.  Most of the restaurants were located in California.  During the period Good Earth operated widely, it was "probably the most prominent chain example of a health-food concept", according to industry trade journal "Nation's Restaurant News".  It was based in California at the time of the purchase by General Mills.  Their tea supplier still exists as Good Earth Teas.  Two restaurants remain in Minnesota that operate under the ownership of Parasole Restaurant Holdings, one located in the Minneapolis suburb of Edina and the other in the St. Paul suburb of Roseville.

Happy Meal (disambiguation): A Happy Meal is a type of kids' meal served at McDonald's.

Supporting paragraphs: Happy Meal McDonald's
Answer: 1940