How did president James K. Polk contribute to nationalism during the mid 1800s?

President James K. Polk significantly contributed to nationalism during the mid-1800s by aggressively pursuing territorial expansion, which was rooted in the belief of Manifest Destiny—the idea that the U.S. was destined to expand across the continent. His administration oversaw the annexation of Texas and the acquisition of Oregon and California following the Mexican-American War. These actions not only increased U.S. territory but also fostered a sense of national pride and identity, as Americans celebrated their growing influence and power on the continent. Polk's policies and achievements solidified a nationalistic spirit that emphasized American exceptionalism and expansionism.