Monopoly

The Basics:

Monopoly, published in 1935 by Parker Brothers, was brought to the company by Charles Darrow.

Why Monopoly is Part of the Games Timeline:

Monopoly is an ingrained part of American culture, and it's also widely known around the world.

Here are the other games I believe are the most culturally and historically significant games published since 1800.

Monopoly Resources:

How to Win Monopoly
Monopoly 101
Monopoly Here and Now: The World Edition
Monopoly - Main Index

More About Monopoly:

Monopoly has a complex history. It was based on The Landlord's Game (1904), designed and patented by Elizabeth Magie.

The goal of the game is to force all of the other players into bankruptcy by buying real estate, building houses and hotels, and charging rent. The influence of Monopoly can be seen in game collections and retail stores all over the world -- more than 200 million games have been sold worldwide, and it's been been published in 26 languages.

By my estimation, Monppoly is also the most copied (both authorized and unauthorized) game published since 1800. Monopoly clones pop up all the time and are widely available.