Ralph Waldo Emerson (1803–1882) was considered the greatest American thinker of his day. He grew up in Boston and entered Harvard at the age of fourteen, graduating with honors in 1821. Thereafter, he taught school and then studied for the ministry. In 1829, he was ordained as junior pastor of Boston's Second Church, and in the same year, he married Ellen Tucker, who died sixteen months later of tuberculosis.

With literary friends from Boston, Emerson founded a magazine, The Dial, which became an important vehicle for the Transcendentalist Movement, of which Emerson was a leader. The Transcendentalists, like the English Romantics, believed in a deep spiritual connection between people and nature. The Transcendentalist Movement was based on a fundamental belief in the unity of the world and God. The soul of each individual was thought to be identical with the world—a microcosm of the world itself. The doctrine of individualism developed through the belief in the identification of the individual soul with God. Emerson believed that by attending closely to one's innermost thoughts and feelings, one could glimpse the great spirit of the universe, what Emerson called the "Over-Soul."

Many accused Emerson of subverting Christianity, but his response was that for him "to be a good minister, it was necessary to leave the church." Emerson's philosophy has been called contradictory, but he held strongly to his romantic belief in personal intuition and flexibility. Such beliefs led Emerson to a radical individualism that helped to shape the American spirit. In his own words, "To believe your own thought, to believe that what is true for you in your private heart is true for all men,—that is genius."

Emerson traveled in Europe and, on returning moved to Concord, Massachusetts, which was the first rural artist's colony and the first place to offer a spiritual and cultural alternative to American materialism. There he married Lydia Jackson, with whom he had four children. During their fifty years of marriage, the Emersons entertained at home many of the leading intellectuals of the day, including their neighbors the Alcotts and Henry David Thoreau. Today, Emerson's house in Concord remains a place of literary pilgrimage. Emerson himself has become a symbol of American optimism and independent thinking. His prose-poetry has influenced a long line of American poets, including Walt Whitman, Emily Dickinson, Edwin Arlington Robinson, Wallace Stevens, Hart Crane, and Robert Frost.