After coming of age, Manning settled down on Old Manse to a life of a yeoman farmer, marrying a woman named Sarah and raising 10 of their 13 children on the farmstead.
On April 19, 1775, while serving in Captain Solomon Pollard’s minutemen company at age of 27, he responded too late to the alarm raised by Patriots during the Battles of Lexington and Concord.
[5] At first, he found himself unable to support a free government and to write his ideas on it, thinking that he would never have to take a stand against tyranny; this changed after the signing of Jay’s Treaty in 1794.
Though it met much criticism, President George Washington pushed for its ratification and Jay's Treaty passed the United States Senate in June 1795.
[9] As academics Jennifer Mercieca and James Arnt Aune noted in their article A Vernacular Republican Rhetoric: William Manning's Key of Libberty, historian Thomas Gustafson would refer to Jay's Treaty as one of the great controversies of the 1790s and as part of a "Thucydidean moment," a point "where a republic confronts the reality that political and linguistic disorders are one in the same.
He also sent American missionaries overseas for negotiations without legislative approval[12] and pretended, in Manning's opinion, to cater to the needs of non-elite and working citizens, the majority, by promoting free trade and increasing demand during America’s involvement in European wars.
Manning distinguished the Few as the small group of elite, rich and powerful men that held the fate of the country in their hands and the Many, including himself, as those facing economic and educational setbacks, not being able to have their voices heard due to their limited circumstances.
[16] Manning wrote in his text, "For instance if the prices of labour & produce should fall one halfe if would be just the same to the few as if their rents fees & salleryes ware doubled, all which they would git out of the many.
[22] Throughout the text, Manning also explained that the Many feared that the Few would form an elite society backed by a federalist government that would shun the Jeffersonian Republican Party and its ideas.
[26] Daniel Shays, a former leader of the revolutionary militia, responded by leading an uprising in Western Massachusetts, closing the courts and preventing seizure of property.
[28] By living in close proximity, Manning gave an eye-witness account of the experience and asked the Many to form organized groups of labor and interests to prevent such happenings in the future.
His beliefs and actions as president, however, were often overshadowed by Adams’ eleventh hour appointment of John C. Marshall, a Federalist, as Chief Justice of the Supreme Court.
[32] On October 21, 1814, shortly before the Hartford Convention, of which the Federalist Party would ultimately meet its demise, William Manning died of an unknown cause on his farm in Hampden.
[34] The Key of Liberty would not be published until 1922 with a foreword by Harvard University historian Samuel Eliot Morison, in which he said, "It used to be said of him by his friends that if William Manning drowned, they would seek his body up-stream, for he would surely not float down with the current like other people.