Philadelphia HGS Director Richard Biddle offered a well-documented presentation on the facts of Monopoly at the Philadelphia conference. The following summary appears at the Philly HGS’s website:
In the early years of the twentieth century, a 38-year old suffragette, actress and inventor named Lizzie J. Magie patented a board game she and others designed and played to demonstrate the effect of the laws of political economy as taught by Henry George. This was The Landlord’s Game.
Notice how this game clearly resembles the modern Monopoly in many respects. Over the course of the next several years, the game board was improved and refined. The rules provided an option to introduce changes in taxation policy based on Henry George’s principles.
The 1910 version of The Landlord’s Game was the first printed and mass-produced version (as far as is known). Although Lizzie Magie held the patent, her motivation for developing the game was educational rather than financial. She hoped those who played the game would come to recognize the unjust nature of existing socio-political arrangements and institutions and at the same time come to appreciate the wisdom of Henry George’s proposed changes to the system.
Another game created by Lizzie Magie, called Mock Trial, was produced in 1910 by Parker Brothers. There is some evidence that Lizzie Magie actually met George Parker a few years earlier, and we can reasonably assume George Parker was well aware of Lizzie’s attachment to Henry George’s principles.