Over time, slavery became more institutionalized and widespread. In ancient Egypt, Greece, and Rome, slavery was a central part of the economy. Slaves were used to build pyramids, temples, and other large-scale projects. They also worked in agriculture, mining, and manufacturing. In the Roman Empire, slaves made up as much as one-third of the population.
Slavery continued to exist in many parts of the world until the 19th century. In the United States, slavery was legal until 1865, when it was abolished by the Thirteenth Amendment to the Constitution. However, slavery still exists in some parts of the world today, although it is illegal in most countries.