The Thirteen Colonies, also known as the Thirteen British Colonies, the Thirteen American Colonies, or later as the United Colonies, were a group of British colonies on the Atlantic coast of North America. Founded in the 17th and 18th centuries, they began fighting the American Revolutionary War in April 1775 and formed the United States of America by declaring full independence in July 1776. Just prior to declaring independence, the Thirteen Colonies in their traditional groupings were: New England (New Hampshire; Massachusetts; Rhode Island; Connecticut); Middle (New York; New Jersey; Pennsylvania; Delaware); Southern (Maryland; Virginia; North Carolina; South Carolina; and Georgia). The Thirteen Colonies came to have very similar political, constitutional, and legal systems, dominated by Protestant English-speakers. The first of these colonies was Virginia Colony in 1607, a Southern colony. While all these colonies needed to become economically viable, the founding of the New England colonies, as well as the colonies of Maryland and Pennsylvania, were substantially motivated by their founders' concerns related to the practice of religion. The other colonies were founded for business and economic expansion. The Middle Colonies were established on an earlier Dutch colony, New Netherland. All the Thirteen Colonies were part of Britain's possessions in the New World, which also included territory in Canada, Florida, and the Caribbean.The colonial population grew from about 2,000 to 2.4 million between 1625 and 1775, displacing Native Americans. This population included people subject to a system of slavery which was legal in all of the colonies prior to the American Revolutionary War. In the 18th century, the British government operated its colonies under a policy of mercantilism, in which the central government administered its possessions for the economic benefit of the mother country.

The Thirteen Colonies had a high degree of self-governance and active local elections, and they resisted London's demands for more control. The French and Indian War (17541763) against France and its Indian allies led to growing tensions between Britain and the Thirteen Colonies. During the 1750s, the colonies began collaborating with one another instead of dealing directly with Britain. With the help of colonial printers and newspapers these inter-colonial activities and concerns were shared and cultivated a sense a united American identity and led to calls for protection of the colonists' "Rights as Englishmen", especially the principle of "no taxation without representation". Conflicts with the British government over taxes and rights led to the American Revolution, in which the colonies worked together to form the Continental Congress. The colonists fought the American Revolutionary War (17751783) with the aid of the Kingdom of France and, to a much smaller degree, the Dutch Republic and the Kingdom of Spain.

John Casor (surname also recorded as Cazara and Corsala), a servant in Northampton County in the Virginia Colony, in 1655 became the first person of African descent in the Thirteen Colonies to be declared as a slave for life as a result of a civil suit. In an earlier case, John Punch was the first man documented as a slave in the Virginia Colony, sentenced to life in servitude for attempting to escape his captors.In one of the earliest freedom suits, Casor argued that he was an indentured servant who had been forced by Anthony Johnson, a free black man, to serve past his term; he was freed and went to work for Robert Parker as an indentured servant. Johnson sued Parker for Casor's services. In ordering Casor returned to his master, Johnson, for life, the court both declared Casor a slave and sustained the right of free black people to own slaves.

Laws racializing slavery hardened during Casor's lifetime. In 1662, the Virginia Colony passed a law incorporating the principle of partus sequitur ventrem, ruling that children of enslaved mothers would be born into slavery, regardless of their father's race or status. This was in contradiction to English common law for English subjects, which based a child's status on that of the father. In 1699 the Virginia House of Burgesses passed a law deporting all free black people. But many new families of free black people continued to be formed during the colonial years by the close relationships among the working class.