Emerson lived and wrote in the days of Westward expansion, religious upheaval, and domestic and international political ferment.
He and his generation grew up during the War of 1812, the Annexation of Texas, the Gold Rush, the Civil War, and the completion of the Union Pacific Railroad. His generation developed a new patriotism, particularly after the War of 1812 when Boston was in constant fear of British invasion. Although the attack never came, many Americans came to share a sense of common life and identity, distinct from European history and customs. His writing reflects the national struggle to develop an American identity during this time, and indeed, many scholars consider his literary style as one of the first uniquely American (in contrast, see the writing of his contemporary, Henry Wadsworth Longfellow, who continued to champion a "European" style).
America was also going through a period of religious upheaval. By the mid-eighteenth century, several ministers in and around Boston began to reject the dominant Calvinist doctrine in favor of a more liberal and positive view of human nature, which placed individual piety and ethical behavior as central to salvation (rather than innate depravity and election to grace). The rejection culminated in not only the split of several of the oldest of the original Puritan churches in New England, but also the creation of the American Unitarian Association in 1825, which would in turn lay the intellectual groundwork for Emerson’s Transcendentalist movement.
Finally, Emerson wrote during a time of political ferment, both internationally and domestically. Europe experienced a series of political revolutions in 1848, driven in part by demands for democracy, beginning with the French Revolution, and immediately spreading to most of Europe and parts of Latin America. In America, tension was building over both the economic inequalities created by the Industrial Revolution, and the continued existence of slavery in the South (which Emerson actively condemned).