<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The history of the United States began with the settlement of Indigenous people before 15,000 BC . Numerous cultures formed . The arrival of Christopher Columbus in 1492 started the European colonization of the Americas . Most colonies formed after 1600 . By the 1770s, thirteen British colonies contained 2.5 million people along the Atlantic coast east of the Appalachian Mountains . After defeating France, the British government imposed a series of new taxes after 1765, rejecting the colonists' argument that new taxes needed their approval (see Stamp Act 1765). Tax resistance, especially the Boston Tea Party (1773), led to punitive laws by Parliament designed to end self - government in Massachusetts . </P> <P> Armed conflict began in 1775 . In 1776, the Second Continental Congress declared the independence of the colonies as the United States of America . Led by General George Washington, it won the Revolutionary War with large support from France . The peace treaty of 1783 gave the new nation the land east of the Mississippi River (except Canada and Florida). The Articles of Confederation established a central government, but it was ineffectual at providing stability, as it could not collect taxes and had no executive officer . A convention in 1787 wrote a new Constitution that was adopted in 1789 . In 1791, a Bill of Rights was added to guarantee inalienable rights . With Washington as the first president and Alexander Hamilton his chief adviser, a strong central government was created . Purchase of the Louisiana Territory from France in 1803 doubled the size of the United States . A second and final war with Britain was fought in 1812, which solidified national pride . </P> <P> Encouraged by the notion of manifest destiny, U.S. territory expanded all the way to the Pacific coast . While the United States was large in terms of area, its population in 1790 was only 4 million . However, it grew rapidly, reaching 7.2 million in 1810, 32 million in 1860, 76 million in 1900, 132 million in 1940, and 321 million in 2015 . Economic growth in terms of overall GDP was even greater . However compared to European powers, the nation's military strength was relatively limited in peacetime before 1940 . The expansion was driven by a quest for inexpensive land for yeoman farmers and slave owners . The expansion of slavery was increasingly controversial and fueled political and constitutional battles, which were resolved by compromises . Slavery was abolished in all states north of the Mason--Dixon line by 1804, but the South continued to profit off of the institution, mostly from production of cotton . Republican Abraham Lincoln was elected in 1860 on a platform of halting the expansion of slavery . </P>

When did the colonies officially become the united states