The billionth burger was served in 1963 on the Art Linkletter TV show. Other milestones, according to the official company history, include 5billion by 1969, 15billion by 1974, and 30billion by 1979.May 3, 2011
https://www.sbsun.com/2011/05/03/mcdonalds-stopped-officially-announcing-burgers-sold-in-1993/
https://www.mashed.com/148375/the-truth-about-how-many-burgers-mcdonalds-has-sold/