From the diverse and complex societies of pre-Columbian Native Americans, through the transformative era of European exploration and colonization, the foundation of the United States evolved significantly. The 13 colonies, established by the English along the Atlantic coast, developed unique regional economies and cultures, with slavery becoming deeply rooted in the South. The Revolutionary War (1775-1783) against British rule resulted in American independence and the creation of a new government under the U.S. Constitution. The early republic faced challenges in establishing a stable political system, expanding westward, and addressing social issues, including the injustices faced by Native Americans and the institution of slavery. These tensions culminated in the Civil War (1861-1865), a devastating conflict that ultimately preserved the Union and abolished slavery. The subsequent Reconstruction era (1865-1877) attempted to rebuild the South and integrate freed slaves into society, but faced significant resistance and ultimately left many of its goals unfulfilled.