This week, game players and enthusiasts from 40 countries will descend upon Las Vegas to compete in the Monopoly World Championship, held roughly every four years. The winner of the Hasbro Inc. -sponsored tournament will take home $20,580 -- the precise sum stashed in the title's make-believe bank.

But one man who is perhaps the game's most obsessive follower won't be attending.

Ralph Anspach, an 83-year-old economics professor, spent decades locked in a real-life battle with Monopoly and its corporate owners. The campaign dented his finances, sent him on a nationwide trek for intelligence and sparked a legal case that reached the steps of the Supreme Court.

Prof. Anspach's woes began with a real-life trademark fight for the right to sell his own game, called Anti-Monopoly. Along the way, he says he helped to publicize the little-known origins of the classic American game.

The official history of Monopoly, a version of which appears on Hasbro's Web site, describes how Charles B. Darrow developed Monopoly during the Great Depression. Parker Brothers, which was later acquired by Hasbro, bought the impoverished heater salesman's patent in 1935 and registered the Monopoly trademark. Since then, the company says, an estimated 750 million copies of Monopoly have been sold worldwide.