Born in New Haven, Connecticut, Ingersoll established a legal career in Philadelphia after graduating from Yale College. The son of British colonial official Jared Ingersoll Sr., Ingersoll lived in Europe from 1773 to 1776 to avoid the growing political conflict between Britain and the Thirteen Colonies. In 1778, having committed himself to the cause of American independence, Ingersoll returned to Philadelphia and won election to the Continental Congress. Ingersoll became convinced of the need for a stronger national government than what was provided by the Articles of Confederation, and he was a delegate to the 1787 Philadelphia Convention. Though he was initially seeking amendments for the Articles of Confederation, he eventually came to support the new Constitution that was produced by the convention.