The Lewis and Clark expedition significantly contributed to American expansionism by exploring and mapping the newly acquired Lousiana Territory. Commissioned by President Thomas Jefferson in 1804, this expedition provided valuable insights into the geography, resources, and native peoples of the region. Their findings spurred interest in westward migration and paved the way for settlement and economic development. By documenting various landscapes and establishing relations with Indigenous tribes, the expedition bolstered the idea of Manifest Destiny and justified American claims over the vast western territories. This ultimately facilitated the nation’s growth across the continent.