The institution of slavery displays a puzzling historical pattern: it is found mostly at intermediate stages of agricultural development, in horticultural societies, and less frequently among hunter-gatherers and societies at more advanced agrarian stages. We explain this rise-and- fall pattern of slavery in a growth model with land and labor as inputs in production. The "organization" of society is determined endogenously, and depends on agricultural technology and population density, both of which also evolve endogenously over time, and depend on how society is organized. The model replicates the full transition of the economy from an egalitarian society with no property rights; to a slave society where a despotic ruler owns both land and people; and finally into a society with a free labor market, where the ruler owns all land but all agents own their labor. In this process, the role of population growth switches from being a force driving the transition into slavery, to a force behind the transition from slavery to free labor. Our model also explains several other historical facts, e.g. why Europeans replaced free labor with slavery following the discovery of the Americas, and why those states in the 19th century US which had sparser population had a larger percentage slaves in the population.
