A delegate to the first Pennsylvania constitutional convention in 1790, and a merchant, he earned a reputation as a frontier leader and had good relations with many Native American in the region.
He was captured by Lenape during Pontiac's Rebellion while trading in the west and was condemned to be burnt, but escaped death when he was adopted by an old Indian woman whose son had died in battle.
[10] Gibson was also appointed a magistrate for Fincastle County, Virginia, which was at that time considered to include Pittsburgh by Connolly in 1775.
In November 1781, David Williamson brought in some Moravian Lenapes captured in Salem, Schoenbrunn and Gnadenhutten, Ohio, to Fort Pitt.
The fact that these were probably done by Half-King and his fellow Wyandots and not by the released Lenape was not factored into account by those who felt to denounce Gibson for this occurrence.
The enlisted men at Fort Pitt then threatened to mutiny, which may have contributed to the conditions that led to the Gnadenhutten Massacre, although it was only one of many factors involved in the situation.
[18] Irvine wrote "a thousand lies are propagated against [Gibson] … occasioned by his unhappy connection with a certain trube, which leads people to imagine that he has an attachment to Indians in general.
"[19] After the war Gibson returned to being a merchant but he went bankrupt, partly due to debts he had incurred in supporting the campaign of George Rogers Clark.
After Harrison arrived in the territory, Gibson took on several more positions after being appointed justice of the peace, Knox County recorder, and a judge of the low court that tried misdemeanors and petty crimes.
Gibson's relationship with the local tribes proved invaluable to Harrison during the numerous treaty negotiations in the early part of his term.
Gibson, who spoke several of the native languages, was the first to become aware of Tecumseh's attempt to massacre the citizens of Vincennes in 1810 and was able to quickly and secretly gather together soldiers to prevent the situation from escalating.
The American Indian Confederacy led by Tecumseh began to make aggressive movements and attacked Fort Harrison.
[22][23] After completing his term in government, at age seventy-six Gibson and his wife Ann returned to private life, briefly remaining in Vincennes.
He returned to live with his daughter and son-in-law, George Wallace, in Braddock's Field near Pittsburg, where he died on April 10, 1822, at age eighty-two, having suffered two years from an "incurable cataract".