His participation in the First Continental Congress at Philadelphia in the fall of 1774 marked the beginning of John Adams' career as an American statesman. He spent much of the next three years as a member of the Second Continental Congress, where his influence was apparent in such important developments as the election of George Washington to be commander in chief, the recommendation that the colonies establish state governments, the decision for independence, and the establishment of the diplomatic service. His hurried visits home from Philadelphia brought urgent demands on his time from the revolutionary government of Massachusetts. When Congress appointed him one of the commissioners to France, he abandoned thoughts of reopening his law practice and set sail in February 1778. Returning home after eighteen months abroad, he became the principal draftsman of the Massachusetts Constitution of 1780, which was to be an important model for the United States Constitution. But before the Massachusetts convention had completed its work, Congress sent him back to Europe to negotiate peace with Great Britain.
Congress appointed additional peace commissioners in 1781, but only Benjamin Franklin and John Jay arrived in time to join Adams in negotiating the Treaty of Paris (1783), by which Great Britain acknowledged American independence and awarded generous boundaries to the new nation. Adams' wife then joined him, and he remained in Europe until 1788, serving as the first American minister to the British court and saving the credit of the United States by negotiating loans from the Netherlands. He returned home the year after the Constitutional Convention of 1787 uncertain of how, if at all, the country would use his unequaled experience in diplomacy and republican government.