Channing was making a stop in New York while traveling to Baltimore to preach the famous sermon in which he would articulate the distinctive tenets of Unitarian Christianity, the most salient of which were the rejection of the Trinity in favor of absolute Monotheism, and the imperative to interpret the Bible through reason.

The task of recruitment was difficult since few ministers could be persuaded to venture away from the stability of the Unitarian heartland in New England and risk their careers in new congregations beyond.

"[1] In partnership with minister Henry Whitney Bellows, who served for over four decades from 1839 to 1882, All Souls grew to include some of the leading social reformers and cultural figures of the city, such as Peter Cooper, Herman Melville, and others.

One noted member was the novelist Catharine Sedgwick, who remarked upon the diverse backgrounds of the people who were attracted to the freedom of ethical inquiry which All Souls offered: "strangers from inland and outland, English radicals and daughters of Erin, Germans and Hollanders, philosophic gentiles and unbelieving Jews .

In evolving from its roots in Unitarian Christianity, All Souls has embraced an enlarging religious pluralism that continues to this day.