Theological Universalism During the American Founding:

I came across this on google books that discusses the universal salvation v. eternal damnation controversy, written in 1848. It references universalists, both unitarian and trinitarian, during the American Founding era.

A taste:

In the United States, it is well known there have been many believers in Universal Salvation, aside from the Universalist denomination. Some of the most eminent men in the days of our Revolution, adopted that sentiment. Among them may be enumerated Gen. Green, who appointed Rev. John Murray, the first preacher of Universalism in America, as Chaplain of the Rhode Island Brigade. Some of the orthodox clergymen remonstrated against this appointment. But Gen. Washington confirmed it, and in General Orders, directed that Mr. Murray "be respected accordingly!" Dr. Benjamin Rush, one of the signers of the Declaration of Independence, was a warm and open Universalist; as was also his friend, the eminent Dr. Redman, of Philadelphia. Of the celebrated Dr. Franklin, his daughter, Mrs. Black, writes as follows: "In his opinion, no system of faith in the christian world, was so well calculated to promote the interests of society, as the doctrine which showed "a God reconciling a lapsed world to himself." Belonging to the orthodox clergy, of about the same period, were Dr Charles Chauncey, of Boston, Dr. John Tyler, of Norwic' Conn., and Dr. Joseph Huntington, of Coventry, Conn., who we all believers and defenders of Universal Salvation.

Here are the general orders where Washington defends John Murray. Here is a post where I reproduce where Washington praised a Universalist Church, indeed, John Murray's particular church (a church that the uber-orthodox considered "infidel"). Here is the letter on google books, with Washington's address reproduced below:

GENTLEMEN,

I thank you cordially for the congratulations, which you offer on my appointment to the office I have the honor to hold in the government of the United States.

It gives me the most sensible pleasure to find, that, in our nation, however different are the sentiments of citizens on religious doctrines, they generally concur in one thing; for their political professions and practices are almost universally friendly to the order and happiness of our civil institutions. I am also happy in finding this disposition particularly evinced by your society. It is, moreover, my earnest desire, that all the members of every association or community, throughout the United States, may make such use of the auspicious years of peace, liberty, and free inquiry, with which they are now favored, as they shall hereafter find occasion to rejoice for having done.

With great satisfaction I embrace this opportunity to express my acknowledgments for the interest my affectionate fellow-citizens have taken in my recovery from a late dangerous indisposition; and I assure you, Gentlemen, that, in mentioning my obligations for the effusions of your benevolent wishes in my behalf, I feel animated with new zeal, that my conduct may ever be worthy of your favorable opinion, as well as such as shall, m every respect, best comport with the character of an intelligent and accountable being.