The first great expansion of the country came with the Louisiana Purchase of 1803, which doubled the country's territory, although the southeastern border with Spanish Florida was the subject of much dispute until it and Spanish claims to the Oregon Country were ceded to the US in 1821. In time, these grants were ceded to the federal government. This land was organized into territories and then states, though there remained some conflict with the sea-to-sea grants claimed by some of the original colonies. This effectively doubled the size of the colonies, now able to stretch west past the Proclamation Line to the Mississippi River. Their independence was recognized by Great Britain in the Treaty of Paris of 1783, which concluded the American Revolutionary War. The union was formalized in the Articles of Confederation, which came into force on March 1, 1781, after being ratified by all 13 states. In the Lee Resolution of July 2, 1776, the colonies resolved that they were free and independent states. The United States of America was created on July 4, 1776, with the Declaration of Independence of thirteen British colonies in North America. US Census Bureau map depicting territorial acquisitions, 2007
