1820s

The 1820s, spanning the years 1820 through 1829, was a decade marked by political realignment, decolonization movements, technical progress, and cultural change. It continued the aftermath of the Napoleonic era, with liberal and nationalist currents challenging established monarchies in parts of Europe, the Americas expanding their autonomous national identities, and industrial capacities expanding in Britain and, increasingly, North America.

In the Americas, the decade featured significant shifts in sovereignty and policy. The United States addressed regional tensions with the Missouri Compromise of 1820, which admitted Missouri as a slave state and Maine as a free state while drawing a line to limit the expansion of slavery north of 36°30′. In 1823, the United States articulated the Monroe Doctrine, warning European powers against further colonization in the Americas. Latin American nations continued consolidating independence movements; Brazil declared independence from Portugal in 1822, establishing the Empire under Dom Pedro I, while Mexico had already achieved independence in 1821. Infrastructure developments such as the Erie Canal, completed in 1825, connected the U.S. interior with the Atlantic coast and spurred regional growth.

In Europe and the wider world, the decade saw the Greek War of Independence begin in 1821, drawing international attention and involvement. Russia experienced the Decembrist Revolt in 1825, a failed bid to impose constitutional reform after the death of Alexander I. The United Kingdom enacted Catholic Emancipation in 1829, removing many restrictions on Catholics and enabling broader political participation. Industrial and transportation innovations also accelerated, with the Stockton and Darlington Railway opening in 1825 and the Rainhill Trials of 1829 advancing steam locomotive technology, signaling the early stages of a railway era. The era’s cultural currents were dominated by Romanticism, which influenced literature, music, and the arts alongside ongoing scientific and geographical exploration.