Post-Revolutionary War years
When the war ended in 1783, Cornplanter recognized the need to develop a positive diplomatic relationship with the fledgling government of what the Haudenosaunee called the "Thirteen Fires." He became a negotiator in disputes between the new "Americans" and the Seneca. He was a signatory of the Treaty of Fort Stanwix (1784), although this treaty was never ratified by the Haudenosaunee.
During the Northwest Indian War, Native Americans in what is now Ohio and Indiana mounted a resistance to the encroachment of American settlers into their territory. Cornplanter convinced the Seneca to remain neutral in this conflict. In addition, he attempted to negotiate with the Shawnee on behalf of the United States.
In 1790, Cornplanter and other Seneca leaders travelled to Philadelphia to meet with President George Washington and Pennsylvania Governor Thomas Mifflin and protest the treatment of their people. Cornplanter extracted an agreement from Washington and Mifflin to protect Seneca land.
Cornplanter made a number of trips to Philadelphia, and later Washington, to strengthen relationships and meet with those who were interested in his people. He tried to understand Euro-American culture, as he felt it necessary for successful relations between the Haudenosaunee and the United States.
Cornplanter was particularly impressed by the beliefs and practices of the Quakers. Like the Quakers, Cornplanter and his half-brother, the religious leader Handsome Lake, strongly opposed the use of liquor, and unlike other Protestant groups, the goal of Quaker missionaries was to educate rather than convert. Cornplanter invited Quakers to the Cornplanter Tract to help the Seneca learn new skills such as animal husbandry, carpentry and smithing as they could no longer rely on hunting or the fur trade as a way of life. He also encouraged Seneca men to become involved in growing crops, a task which traditionally was done by women.
In 1794, Cornplanter was a signatory to the Treaty of Canandaigua. The treaty proclaimed "peace and friendship" between the United States of America and the Haudenosaunee, and affirmed their land rights in the state of New York.
Three years later he signed the Treaty of Big Tree that established Seneca reservations within their traditional territory.
Eventually, Cornplanter became disillusioned with his relationship with the Americans. To fight the drunkenness and despair suffered by many Indians, his half-brother Handsome Lake preached that the Seneca must return to the traditional way of life and take part in religious ceremonies. Cornplanter heeded Handsome Lake's prophecy that they should return to traditional ways and turn away from European assimilation. He burned his military uniform, broke his sword, and destroyed his medals. He closed the schools but did not completely break relations with the Quakers as he retained his respect for them.
Cornplanter occasionally openly expressed his disdain for whites. Upon taking a short ride on the first steamboat to navigate the upper Allegheny River, Cornplanter, while generally impressed with the boat, quipped that "white men will do anything to avoid using their muscles."
During the War of 1812, Cornplanter did not play an active role in the fighting along the Niagara River, however, his son Henry and his nephew Chainbreaker, also known as Blacksnake actively supported the Americans.
As Cornplanter aged, his influence among the Seneca dwindled in favour of Chainbreaker and Red Jacket. He died in 1836 at his home in the Cornplanter Tract.
