The truth is, in the beginning, there was no monopoly on the game because there were so many versions of it. They were created on a ‘local’ basis, using the streets and features of individual cities, and in all likelihood, very few of the inventors aware that anyone else had the same idea.

One of the most notable, was the game created by Lizzie Magie in 1904. It was called the ‘Landlord’s Game’, and was designed to teach people the reality of economics, and how landlords got richer, while tenants got poorer. Lizzie patented the game but it was not produced commercially until 1910. In 1924, now married, Lizzie re-patented the game and named some of the streets for places in Chicago. The game gained in popularity, and other versions began to appear, including Daniel Layman’s edition, which was based on his hometown of Indianapolis, Indiana. That game was licensed to the Knapp Electric Company.
Then in 1934, Charles Darrow of Germantown, Pennsylvania, brought what he claimed was his invention to Parker Brothers—a game based on his city, with pieces and boards hand manufactured by his family.
Parker Brothers, recognizing a good thing when they saw it, bought the game from Darrow, and then went about purchasing the patents and rights to all the other versions, so they could have a true monopoly on Monopoly.
Today, it is the best-selling board game in the world, having surpassed 200 million units.