Transcendentalism

Historically, Transcendentalism began in the mid-1830s and was a split from Unitarianism (which had become an official religion in 1825). Ralph Waldo Emerson was actually a Unitarian minister and nearly all of the early participants were Unitarians. 

Theologically, both Transcendentalism and Unitarianism renounced the Trinity and both were anti-Calvinists in that regard. However, the Transcendentalists took it one step further, and suggested that there may have been no real miracles performed by Jesus. The only great miracle was the planet itself according to Emerson. 

Some of the great 19th century American thinkers were Transcendentalists. Emerson, Thoreau, Margret Fuller (and several other important women of that century), Theodore Parker, and Elizabeth Peabody. Others were heavily influenced by these thinkers including Walt Whitman and Nathaniel Hawthorne. 

How was Transcendentalism different from Deism? Theologically, the differences were almost invisible. However, Transcendentalism had its roots in an actual church-going denomination whereas Deism was mostly a philosophical framework that had no congregational history or theology of its own. 

One historian has made a unique comparison between New England in the 1840s and radical movement of the 1960s counter-culture. The Transcendentalists, like the social radicals of the 60's, were instruments of real social change. Many became strong abolitionists. Elizabeth Peabody was instrumental in transforming early childhood education. Thoreau is still the father of the environmental movement. Communes of Transcendentalists popped up throughout New England. 

Like the 60's counter culture, these people had no disciplined national structure or hierarchy in the 1840's 50's and could not maintain the movement after the Civil War. Although many were great friends and supported each others causes, they met only a few times a years and had no structured congregation themselves. 

Most of the original leaders have left us some of the greatest 19th century literature. Publications by Emerson, Thoreau, Whitman, Hawthorne, remain some of the best works of the 19th century.

Reference: "Head and Heart," by Garry Wills, 2008, p.264