What tax on land value did Henry George advocate in Progress and Poverty?

Henry George advocated a land value tax in his 1879 book Progress and Poverty.

George argued that the value created by a community should benefit the community rather than accrue entirely to private landowners. His proposal focused on the unimproved value of land—the value of the location itself—rather than buildings, machinery, or other improvements placed on it.

This idea is often called the single tax because George believed a sufficiently large land-value levy could replace many other taxes. His arguments influenced reformers, political movements, and economists in several countries, although governments generally did not adopt his full single-tax program.

A land value tax is different from an ordinary property tax. Property tax usually covers both land and buildings, while land value tax aims to tax only the site value. Supporters say this encourages productive use of land; critics debate valuation, implementation, and effects on landowners.