Manifest Destiny was part of a broader upwelling of liberalism in the 19th century. The Mexican-American War was seen by its enthusiasts as of a piece with the democratic revolutions that spread across Europe in 1848, the same year the war concluded. As the historian Steve Widdmer has noted, Whitman announced the arrival of a “holy millennium of liberty.” Melville suggested that “the political Messiah had come.”
Such a reaction is startling to present-day readers who have been taught to see the Mexican-American War as one of illiberal conquest. But the historians Stephen Hahn and Frederick Merck have established that Manifest Destiny’s proponents hoped to achieve a network of independent states, voluntarily affiliated. This is a very different picture than that presented by Franklin Foer when he likens Trump’s supposed doctrine of Manifest Destiny to “a Hobbesian world in which the most powerful are given free rein to dominate.”
Young America took up more ideas than expansion and popular sovereignty. Young American politicians embraced the “free land” idea of George Henry Evans, a radical reformer associated with Marx and Engels. Evans, in turn, would eventually change the name of his magazine The Working Man’s Advocate to Young America. The “free land” idea called for distributing western lands to settlers to ease the plight of workers in the crowded cities of the east. Ultimately, this reform was achieved through the passage of the Homestead Act. This radical egalitarian measure served the project of an expanding democratic republic overspreading the continent.
Young America, of course, flourished on the brink of the Civil War, unbeknownst to its followers. The annexation of Mexican territory accelerated the war by opening the question of whether the new territories would be slave or free. The Young American policy of popular sovereignty, encoded in Stephen Douglas’s Kansas-Nebraska Act, brought the war closer. Popular sovereignty as applied to slavery meant letting the settlers of each new state vote on whether it would be slave or free. In the Kansas-Nebraska territory, violent clashes between slaveholders and “free soilers” ensued. It was in these battles that John Brown got his start as a militant. Some enthusiasts of the act believed it would ultimately end slavery, as liberty would win out in a free democratic contest. In a sense, they were right, but the route from popular sovereignty to emancipation was more tortured and bloody than they could have imagined. Ultimately, the ideas of Young America and the dream of Manifest Destiny would be utterly eclipsed by sectionalism and the Civil War.