Behind every great man is a whole team of people being denied credit and royalties
I stumbled across this interesting article about Elizabeth Magie, the inventor of a proto-Monopoly game called the Landlord's Game. The article calls her the true inventor of Monopoly, but per a Wikipedia article, there are 5 other people who invented elements of modern Monopoly as well.
However, for a long time, Charles Darrow was the only man credited with inventing Monopoly. Darrow didn't actually invent any of the Monopoly rules. He created pretty game boards and sold them and eventually took credit for the game, but he simply used the rules that a friend taught him. I'm unclear on whether he contributed anything to the design beyond hiring graphic designers to design nicer icons. His family helped create the initial boards that he sold.
Elizabeth Magie apparently protested at the time, and it seems like it wouldn't be hard for Parker Brothers to have revised their marketing strategy to include credit for both Magie and Darrow. They bought Magie's patent off her to consolidate control over Monopoly. But they didn't. Darrow was given and took sole credit. He also is the only one who became a millionaire from the game.
The only reason the myth of the sole creator was revealed was because Parker Brothers sued Professor Ralph Anspach over marketing his response game, Anti-Monopoly.
Jesse Raiford, Ruth Hoskins, Louis and Ferdinand Thun, and Daniel Layman are the other people Wikipedia credits with developing Darrow's Monopoly. Per The Antiques Almanac website (http://theantiquesalmanac.com/monopoly.htm
), Ruth Hoskins drew the first Atlantic City monopoly board, which was the board that Darrow copied. I haven't been able to find out information about the other ones.