American Revolutionary War: Representatives from the Thirteen Colonies begin the Second Continental Congress in Philadelphia.

The Second Continental Congress was a meeting of delegates from the Thirteen Colonies in America that united in the American Revolutionary War. It convened on May 10, 1775, with representatives from 12 of the colonies in Philadelphia, Pennsylvania, shortly after the Battles of Lexington and Concord, succeeding the First Continental Congress which met in Philadelphia from September 5 to October 26, 1774. The Second Congress functioned as a de facto national government at the outset of the Revolutionary War by raising armies, directing strategy, appointing diplomats, and writing petitions such as the Declaration of the Causes and Necessity of Taking Up Arms and the Olive Branch Petition. All thirteen colonies were represented by the time the Congress adopted the Lee Resolution which declared independence from Britain on July 2, 1776, and the congress agreed to the Declaration of Independence two days later.

Afterward, Congress functioned as the provisional government of the United States of America through March 1, 1781. During this period, its achievements included: Successfully managing the war effort; drafting the Articles of Confederation and Perpetual Union, the first U.S. constitution; securing diplomatic recognition and support from foreign nations; and resolving state land claims west of the Appalachian Mountains.

Many of the delegates who attended the Second Congress had also attended the First. They again elected Peyton Randolph to serve as President of the Congress and Charles Thomson to serve as secretary. Notable new arrivals included Benjamin Franklin of Pennsylvania and John Hancock of Massachusetts. Within two weeks, Randolph was summoned back to Virginia to preside over the House of Burgesses; Hancock succeeded him as president, and Thomas Jefferson replaced him in the Virginia delegation. The number of participating colonies also grew, as Georgia endorsed the Congress in July 1775 and adopted the continental ban on trade with Britain.

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 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 (1754–1763) 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. These inter-colonial activities cultivated a sense of shared 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 (1775–1783) with the aid of the Kingdom of France and, to a much smaller degree, the Dutch Republic and the Kingdom of Spain.