International trade, they are one of the biggest trade countries in the world so that makes sense:)
The Gulf of Tonkin Resolution or the Southeast Asia Resolution, Pub.L. 88–408, 78 Stat. 384, enacted August 10, 1964<span>, was a joint resolution that the United States Congress passed on </span>August 7, 1964<span>, in response to the Gulf of Tonkin incident.</span>
A primary occupation was farming
Treaty of Paris, 1783. The Treaty of Paris was signed by U.S. and British Representatives on September 3, 1783, ending the War of the American Revolution. Based on a1782 preliminary treaty, the agreement recognized U.S. independence and granted the U.S. significant western territory. Remember this was a very important treaty.