Manifest Destiny was the belief promoted by Democratic politicians such as James K. Polk that it was inevitable that the American people would create a nation from the Atlantic Ocean to the Pacific Ocean. The goal was to promote Jacksonian Democracy by expanding the lands available to yeomen farmers and slave plantation owners. Conservatives at the time, led by the Whig Party, strongly rejected the doctrine and instead said that America's future was in modernization, urbanization and industrialization. Henry Clay and Abraham Lincoln were leading Whigs who spoke out against manifest Destiny, especially when it entangled the U.S. in a war with Mexico in 1846.
The secret Ostend Manifesto, written in 1854 by the U.S. ambassadors to Spain, France, and Britain was essentially a plan for the United States to purchase Cuba from Spain. Southern Democrats hoped the acquired island would become another slave state, and that future acquisitions would negate northerners' efforts to prevent the spread of slavery.
When the Ostend manifesto became public, antislavery northerners, denounced the agreement and the plan never went into effect. In 1844 James K. Polk, an expansionist Democrat defeated Henry Clay, a Whig who rejected expansion. "Fifty-Four Forty or Fight!" became a catchphrase for the annexation of the entire Oregon Country, then co-owned with Britain. The slogan referred to the region's northern boundary of 54°40ʹ N latitude (that is, the southern boundary of Alaska). The U.S. and Britain reached a compromise, splitting the region in half along the 49th parallel, which forms to this day marks the US-Canada. Polk also added the new state of Texas to the Union, and after winning the Mexican-American War, purchased New Mexico, Arizona and California as well. Whigs vehemently opposed his war and his expansion plans.
- Belohlavek, John M. et al. Manifest Destiny and Empire: American Antebellum Expansionism (1998) excerpt and text search
- Heidler, David S. and Jeanne T. Heidler. Manifest Destiny. (2003).
- Hietala, Thomas. Manifest Design: American Exceptionalism and Empire, 2003. Previously published as Manifest Design: Anxious Aggrandizement in Late Jacksonian America, 1985.
- McDougall, Walter A. Promised Land, Crusader State: The American Encounter with the World Since 1776. (1997) by a conservative historian
- Merk, Frederick. Manifest Destiny and Mission in American History: A Reinterpretation. (1963).
- Morrison, Michael A. Slavery and the American West: The Eclipse of Manifest Destiny and the Coming of the Civil War (1997).
- Stephanson, Anders. Manifest Destiny: American Expansionism and the Empire of Right (1995)
- Tuveson, Ernest Lee. Redeemer Nation: The Idea of America's Millennial Role. (1968).
- Weinberg, Albert K. Manifest Destiny: A Study of Nationalist Expansionism in American History. (1935), history of the idea