Georgism is concerned with the distribution of economic rent caused by natural monopolies, pollution, and the control of commons, including title over natural resources and other contrived privileges. It is an economic philosophy developed by American 19th century economist Henry George, the primary focus of which is the “Single Tax”, eliminating all other taxes, on land values, most notably a ‘Land Value Tax’. It proved to be an entry point for some into either Progressivism or Libertarianism, as many founders of both movements got their start as political activists as Georgists.