As the United States prepares to celebrate its 250th anniversary, historians are looking back at the founding-era documents that helped define the nation's earliest ideals. 

Among them is a little-known 1790 exchange between John Carroll, the first Catholic bishop in the United States, and President George Washington — a correspondence that helped answer a fundamental question facing the young republic: Could Catholics, long viewed with suspicion under British rule, truly become equal American citizens?

The answer still rests today inside the Library of Congress.

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About 50 feet from Dr. Kevin Butterfield's office in the Library's Manuscript Division sits the original letter Carroll sent to Washington, preserved among the George Washington Papers.

Washington "was spending the entire year of 1790, more or less, connecting with the entire nation," said Butterfield, acting chief of the Library of Congress Manuscript Division. "He connected with the people because he believed that it was important as the new president that they interact directly with him and have a chance to see the new government in action."

As Washington traveled through the states during his first year in office, letters poured in from religious congregations, civic organizations and local communities seeking reassurance about their place in the new federal government. Among them was a March 1790 address from John Carroll, who became the first Catholic bishop in the United States after the Vatican established the nation’s first diocese in Baltimore in 1789, and other Catholic leaders asking whether Catholics — long viewed with suspicion under British rule — would be fully included in the new republic.

Michael Breidenbach, dean of the Honors College at Ave Maria University, said the exchange also reminds Americans that Catholics were not merely beneficiaries of the nation's founding — they helped shape it.

"As America approaches its 250th anniversary, there is a heated debate about whether the nation's foundation had Protestant, secular or other roots," he said. "Often missing from these conversations are the Catholic contributions to the American founding."

Carroll's letter, Butterfield said, stood out because it sought reassurance that Catholics would be fully included in the new republic.

"They were sharing their thoughts about religious liberty and the importance of having a nation where they were included as full citizens," he said.

Catholic priests had ministered in the American colonies for generations, but until the Vatican established the Diocese of Baltimore in 1789, there had been no Catholic bishop in the United States. Carroll was consecrated the following year, becoming the country's first bishop.

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Reading from the original manuscript, Butterfield pointed to the passage that captured the Catholics' appeal:

"Whilst our country preserves her freedom and independence, we shall have a well-founded title to claim from her justice equal rights of citizenship as the price of our blood spilt under your eyes and of our common exertions for her defense."

The words reminded Washington that Catholics had fought beside him throughout the Revolutionary War.

"Carroll's remembering eight years of George Washington's service as commander in chief through the bloody war for independence and saying, as Washington fully knew, Catholics were a part of that battle from the start and served under his leadership to win independence," Butterfield said.

For centuries before the American Revolution, Catholics in England and many of its colonies faced sweeping restrictions.

"It's important to understand that many English people and colonists mistrusted Catholics," said Catherine O'Donnell, a historian at Arizona State University. "They were thought to be loyal to Rome rather than to their countrymen, and to lack independence of mind."

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Catholics were barred from holding office in many places, prevented from voting, required to swear oaths rejecting papal authority and, in some colonies, prohibited from openly practicing their faith.

Carroll experienced that discrimination firsthand. As a child, he was sent to Europe for a Catholic education because such schooling was unavailable to him in Maryland. He later joined the Jesuits, a Catholic religious order known for education, missionary work and scholarship. While Jesuits later became deeply rooted in American Catholic life, Carroll’s formation had to take place overseas because Catholic institutions in the colonies were still sharply limited.

Yet rather than seeking a return to an established Catholic state, Carroll believed the new American republic offered something better.

"He thought the separation of church and state was a good thing," O'Donnell said.

The letter to Washington was sincere, she said, but also carefully calculated.

"Carroll admired Washington throughout Washington's life," O'Donnell said. "This letter was sincere and also in a way strategic: Carroll wanted Washington to publicly affirm Catholics' welcome place in the new nation."

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If the letter was a test, she added, it was one Carroll expected Washington to pass.

Carroll was joined by several of the young nation's most prominent Catholic leaders. The address was signed by his cousin Charles Carroll of Carrollton — the only Catholic signer of the Declaration of Independence — as well as his relative Daniel Carroll, a signer of the U.S. Constitution, and Congressman Thomas FitzSimons of Pennsylvania. Together, they argued that American Catholics had earned the same rights of citizenship through their contributions to the Revolutionary War and the nation's founding.

"American Catholics' remarkable transformation — from being suspected subjects of a king to being trusted citizens of a new republic — is wonderfully illustrated in Bishop John Carroll's 1790 letter to George Washington," said Breidenbach, who is also the author of the book "Our Dear-Bought Liberty: Catholics and Religious Toleration in Early America".

Washington's reply left little doubt where he stood.

He thanked Catholics for the "patriotic part" they had played during the Revolution and wrote that they were already "realizing, instead of anticipating, the benefits of the general Government."

Butterfield said the response reflected Washington's broader vision for the country.

"As long as you demean yourself as a good citizen and follow the laws, it doesn't matter what your religious beliefs are," Butterfield said, summarizing Washington's message. "You're fully a part of the nation."

Washington, Butterfield said, recognized that every public word he spoke helped define the new republic.

"He is fully aware that he is a symbol of the nation, that the words that he speaks have consequences, that every word that he says matters."

Washington expressed the same principle in his correspondence with other minority religious communities, including the Hebrew Congregation in Newport, Rhode Island.

"Washington makes clear that he's not asserting 'toleration,' which would imply that a group of people are being given some kind of special permission to exist and worship," she said. "Rather, all good citizens have the same rights regardless of religion."

Although several states continued to maintain religious restrictions for decades, the new federal government charted a different course.

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Even before the First Amendment was ratified, Article VI of the Constitution prohibited religious tests for federal office. Washington, who had presided over the Constitutional Convention, consistently defended that principle throughout his presidency.

"At the national level from day one, this was an experiment in religious freedom," Butterfield said.

The correspondence itself survived because Washington understood that his papers would matter to future generations.

According to Butterfield, Washington preserved the collection, leaving it to his nephew, Supreme Court Justice Bushrod Washington. Congress purchased the papers in 1834, and they were later transferred from the State Department to the Library of Congress, where they remain today.

The Carroll letter is now one of roughly 77,000 items in the George Washington Papers. While researchers around the world can consult digitized versions, the original manuscript is only brought out in rare circumstances to preserve it.

O'Donnell believes the lesson extends beyond Catholic history.

"I think that it's valuable for Americans to understand that the history of the founding period contains just about everything: ideals such as religious liberty and prejudices, such as those against Catholics," she said.

She also believes the correspondence demonstrates the importance of public leadership.

Washington's belief that good citizenship did not require any particular religious views "seems timely," O'Donnell said, as does Carroll's belief that "public exchanges about important matters can help make ideals part of people's sense of their community, rather than just a theoretical set of rights."

More than two centuries later, the exchange remains more than a forgotten piece of correspondence. It captures an early moment when one of America's smallest religious minorities asked whether the promises of the Revolution truly applied to them — and when the nation's first president answered that they did.