The Iroquois Confederacy is believed to have been founded by the Great Peacemaker at an unknown date estimated between 1450 and 1660, bringing together five distinct nations in the southern Great Lakes area into "The Great League of Peace". Other research, however, suggests the founding occurred in 1142. Each nation within this Iroquoian confederacy had a distinct language, territory, and function in the League.
The League is governed by a Grand Council, an assembly of fifty chiefs or sachems, each representing a clan of a nation.
When Europeans first arrived in North America, the Haudenosaunee (Iroquois League to the French, Five Nations to the British) were based in what is now central and west New York State including the Finger Lakes region, occupying large areas north to the St. Lawrence River, east to Montreal and the Hudson River, and south into what is today northwestern Pennsylvania. At its peak around 1700, Iroquois power extended from what is today New York State, north into present-day Ontario and Quebec along the lower Great Lakes, upper St. Lawrence, and south on both sides of the Allegheny Mountains into present-day Virginia and Kentucky and into the Ohio Valley. From east to west, the League was composed of the Mohawk, Oneida, Onondaga, Cayuga, and Seneca nations. In about 1722, the Iroquoian-speaking Tuscarora joined the League, having migrated northwards from the Carolinas after a bloody conflict with white settlers. A shared cultural background with the Five Nations of the Iroquois (and sponsorship from the Oneida) led the Tuscarora to become accepted as the sixth nation in the confederacy in 1722; the Iroquois became known afterwards as the Six Nations.
Other independent Iroquoian-speaking peoples, such as the Erie, Susquehannock, Huron (Wendat) and Wyandot, lived at various times along the St. Lawrence River, and around the Great Lakes. In the American Southeast, the Cherokee were an Iroquoian-language people who had migrated to that area centuries before European contact. None of these were part of the Haudenosaunee League. Those on the borders of Haudenosaunee territory in the Great Lakes region competed and warred with the nations of the League.
French, Dutch and English colonists, both in New France (Canada) and what became the Thirteen Colonies, recognized a need to gain favour with the Iroquois people, who occupied a significant portion of lands west of the colonial settlements. Their first relations were for fur trading, which became highly lucrative for both sides. The colonists also sought to establish friendly relations to secure their settlement borders.
For nearly 200 years, the Iroquois were a powerful factor in North American colonial policy. Alliance with the Iroquois offered political and strategic advantages to the European powers, but the Iroquois preserved considerable independence. Some of their people settled in mission villages along the St. Lawrence River, becoming more closely tied to the French. While they participated in French-led raids on Dutch and English colonial settlements, where some Mohawk and other Iroquois settled, in general, the Iroquois resisted attacking their own peoples.
The Iroquois remained a large politically united Native American polity until the American Revolution, when the League kept its treaty promises to the British Crown. After their defeat, the British ceded Iroquois territory without consultation, and many Iroquois had to abandon their lands in the Mohawk Valley and elsewhere and relocate to the northern lands retained by the British. The Crown gave them land in compensation for the five million acres they had lost in the south, but it was not equivalent to earlier territory.
Modern scholars of the Iroquois distinguished between the League and the Confederacy. According to this interpretation, the Iroquois League refers to the ceremonial and cultural institution embodied in the Grand Council, which still exists. The Iroquois Confederacy was the decentralized political and diplomatic entity that emerged in response to European colonization, which was dissolved after the British defeat in the American Revolutionary War. Today's Iroquois/Six Nations people do not make any such distinction, use the terms interchangeably, but prefer the name Haudenosaunee Confederacy.
After the migration of a majority to Canada, the Iroquois remaining in New York were required to live mostly on reservations. In 1784, a total of 6,000 Iroquois faced 240,000 New Yorkers, with land-hungry New Englanders poised to migrate west. "Oneidas alone, who were only 600 strong, owned six million acres, or about 2.4 million hectares. Iroquoia was a land rush waiting to happen." By the War of 1812, the Iroquois had lost control of considerable territory.