A&W traces its roots to June 20, 1919, Roy W. Allen opened a root beer stand in Lodi, California. Allen had purchased his root beer recipe from a pharmacist and decided to start selling the drink on a hot summer day that happened to coincide with a city-wide party celebrating the homecoming of local World War I heroes.
Allen’s root beer was a hit and two years later, he partnered with former employee Frank Wright to open additional root beer stands in the area. Around this time, Allen and Wright coined the name A&W, which uses the first letter of both of their last names.
As their success continued, Allen and Wright decided to sell A&W franchises in 1925. This makes A&W the oldest fast-food chain in the world. Over time A&W expanded its menu and added food such as burgers, hot dogs, cheese curds, and other typical fast-food fares.
As of 2019, the chain has approximately 1,000 restaurants (& counting) in the U.S. and international markets.
According to en.wikipedia and awfranchising.com