New England Transcendentalism flowered during a period in American history marked by expansion, change, a growing national self-awareness, and increasing political, social, and regional polarization. The 1830 United States Census recorded a population of 12,866,020. By the 1860 Census, the population had more than doubled, to 31,443,321. The years from 1830 to 1860 witnessed the exploration and annexation of much new territory, westward migration, dramatic improvements in transportation and communication, and development toward party politics as we recognize them today. The North became more urbanized and industrialized, whereas the South remained primarily agricultural, resulting in ultimately irreconcilable disagreement over the issue of slavery, as well as tension over the tariff question.
An idealistic reform impulse exposed and combatted social, political, and economic inequities, slavery foremost among them. The Native American was feared, displaced, romanticized, and made the object of reform efforts. There was a trend toward the democratization of educational and cultural opportunities, and an appetite for popular entertainment on a large scale.
It was the age of the Monroe Doctrine and of "manifest destiny," applied by advocates of territorial expansion to encourage acquisitive government actions. The composition of the population began to change in the 1840s and 1850s, as immigration into the United States increased in the wake of European political upheaval and the potato famine in Ireland, triggering reactionary response from some quarters.
Traditional New England Congregationalism was criticized, Unitarianism arose, and other new, distinctly American religions sprang up. While many Americans maintained a wary distance from, or blissful ignorance of, currents in foreign politics and culture, certain religious leaders and some intellectuals and writers were strongly influenced by foreign philosophy and literature, forging in Transcendentalism a radical expression of European idealism and Romanticism.