From what I can gather the Atari World Championships was the first major national arcade video game contest, held in Chicago in 1981. Apparently, a lot was at stake, as the total prize money was $50,000.
Seller also has a couple of other nice posters, including this Asteroids one.
This poster is unusual in that it was shipped to the amusement games distributor to pass out to video games arcades. The poster was used to keep track of the highest scorer on an Atari video game. The winners at each location could go on to the national championship. The first prize was $50,000.00.