1492: Columbus reaches Americas, sparking European exploration. 1607: English settle Jamestown; colonies grow with British, Dutch, French settlers, plus enslaved Africans. 1776: Independence from Britain; population ~2.5M, mostly European descent with Native and small Black minorities. 1803 Louisiana Purchase doubles size; 1848 Mexican-American War adds Southwest/California via Guadalupe Hidalgo, incorporating ~100K Mexicans into US, boosting Hispanic roots there. Ellis Island (1892-1954) funnels 12M+ Europeans, cementing white majority (~80% by 1900), while westward expansion displaced Natives, shaping today's ~60% white, 19% Hispanic demographics.