[2] During the dispute between Vermonters who held land New Hampshire titles from Benning Wentworth, the colonial Governor, and the government of New York, which tried to make them acquire confirming titles from New York, Clark was a prominent anti-New Yorker, chairing meetings of citizens called to discuss and plan strategy, and preparing written communications to New York's leaders.
[4] Clark was active in the American Revolution, serving as chairman of Bennington's Committee of Satefy.
In addition he served as a Commissary, helping supply the garrison at Fort Ticonderoga, and gathering and organizing the delivery of supplies to the army of Horatio Gates during the Saratoga Campaign.
Isaac Clark married Hannah, one of the daughters of Governor Thomas Chittenden.
He was selected to serve as Speaker of the House after Joseph Bowker resigned in order to accept a seat on the Governor's Council.