William Ellery Channing was the foremost Unitarian preacher in the United States in the early nineteenth century and, along with Andrews Norton , one of Unitarianism's leading theologians. Channing was known for his articulate and impassioned sermons and public speeches, and as a prominent thinker in the liberal theology of the day. His religion and thought were among the chief influences on the New England Transcendentalists although he never countenanced their views, which he saw as extreme. He espoused, especially in his "Baltimore Sermon" of May 5, 1819, given at the ordination of the theologian and educator Jared Sparks as the first minister of the newly organized First Independent Church of Baltimore, the principles and tenets of the developing philosophy and theology of Unitarianism, leading to the organization in 1825 of the first Unitarian denomination in America and the later developments and mergers between Unitarians and Universalists, resulting finally in the Unitarian Universalist Association of America in 1961.
Karen Horney was a German psychoanalyst who practiced in the United States during her later career. Her theories questioned some traditional Freudian views. This was particularly true of her theories of sexuality and of the instinct orientation of psychoanalysis. She is credited with founding feminist psychology in response to Freud's theory of penis envy. She disagreed with Freud about inherent differences in the psychology of men and women, and she traced such differences to society and culture rather than biology. As such, she is often classified as neo-Freudian.