In the first years after the Revolutionary War, the question of who could become a citizen rarely came up on the new country's soil. It was instead asked hundreds of miles offshore, when American sailors were stopped by British ships forced to prove which country they belonged to.
"It's actually a big controversy," said Nathan Perl-Rosenthal, senior research fellow at Harvard University and author of "Citizen Sailors: Becoming American in the Age of Revolution."
"The people who really care about citizenship are sailors, because they're the ones who are out on the ocean having to demonstrate that they are who they say they are," he said. "And so we actually have massive evidence of naturalizations of sailors."
Britain had suffered major economic setbacks due to the Revolutionary War. As trade expanded and a new war with France emerged in the 1790s, the Royal Navy needed more sailors. British authorities also rejected the idea of British-born subjects becoming Americans, thereby escaping naval service.
British merchant vessels often stopped American ships and boarded them in search of sailors they considered British subjects. Distinguishing them wasn't always easy: they often spoke the same language, and many had been born in what was now the United States or Great Britain, although some crews had French, Dutch, and Black sailors. Despite ship records, assessment of goods and interviews, the British navy impressed thousands of sailors into service.
Sailors — including free Black mariners — were among the first to ask: who is an American citizen? And what does it take to become one?
In present day, the questions still resound, but isolationist immigration policies from President Donald Trump have upended the naturalization system and limited who can take the oath of citizenship.
A winding history
In the 150 years before the American Revolution, Britain and its North American colonies tended to use naturalization as a recruitment tool to attract settlers to land taken from Indigenous peoples. They would offer easy naturalization, and the ability to give property to heirs. Group naturalizations in the colonies were common.
Naturalization authority was fragmented, with colonies— and in some places municipalities— granting forms of local citizenship or legal status.
"Perhaps the most fundamental institution in the Royal Colony of New York was the citizen himself … Not only did it possess for him a profound political significance, but it was the condition of his economic independence," wrote Robert Seybolt in the "Colonial Citizen of New York City."
In New York City, applicants paid a fee, took an oath and received a "certificate of freedom," a practice dating back to the 17th century. Without that legal status, a person couldn't vote or run for office, practice certain trades or run a business.
Allegiance and citizenship were catalysts of the American Revolution. Britain banned colonial governors from allowing people to naturalize, colony-by-colony, in 1773. Colonists saw this as an insult that denied them the right to determine who should be part of their community.
The issues stuck in the craw: the grievance against King George III was eventually written into the Declaration of Independence:
"He has endeavoured to prevent the population of these States; for that purpose obstructing the Laws for Naturalization of Foreigners; refusing to pass others to encourage their migrations hither," the document reads.
Citizenship and loyalty
Colonists cared most about the allegiance of their neighbors. Were they traitors, loyal to the King, or allied with the new republic? Massachusetts, for example, deemed anyone who didn't take a loyalty oath fit to be deported, according to the book "Migration and the Origins of American Citizenship," published this year by Anna Law, a political science professor at Brooklyn College.
The years after the American Revolution were tumultuous as the fledging United States established its economy and system of government. Immigration remained relatively limited, due to the new country's poor economy, especially compared with the mass migrations that would come in the 19th century.
In 1780s Massachusetts, free Black residents could be considered state citizens. The state implemented some limitations to prevent waves of escaped slaves from slaveholder states. In 1788, Massachusetts passed legislation saying no African person who was not a citizen of another state could "tarry within" the Commonwealth for more than two months without producing a "certificate from the Secretary of the State of which he shall be a citizen."
Gender created another dividing line in what citizenship meant in practice. Women could be citizens, but lacked many of the political rights associated with citizenship today. Voting was considered a states' issue, and women could not vote because it was widely accepted their husbands represented their interests.
Citizenship based on 'character'
The U.S. Constitution gave Congress the power to establish a "uniform rule of Naturalization," but it did not clarify who qualified for naturalization until the Naturalization Act of 1790. The law allowed a "free white person" who resided in the US for two years and could prove "good moral character" to take an oath. Those individuals could be naturalized in state, local or federal courts, and children of successful applicants automatically became citizens if they were under 21.
"You need people who are morally right — but it is mushy. And it's like nailing Jell-O to a wall trying to explain it," said Law.
"It's like beauty — good moral character is in the eye of the beholder," she added.
Law said very few African Americans were judged to have good moral character, despite giving examples of their contributions. Neighbors would travel to circuit courts and testify to applicants' good character.
"This meant more or less that you were not causing a lot of trouble, you weren't a criminal. It was not a political litmus test in this period. I would say it's more of a neighborly test," said Perl-Rosenthal.
More than two centuries later, the "good moral character" clause remains, and has been emphasized by the Trump administration. Immigrants eligible to apply can demonstrate it by showing they have steady employment, received a degree, have a family, volunteer, and have no criminal record. The US Citizenship and immigration services can also interview neighbors.
States primarily governed who could vote, and the rules varied by state.
"The connection between citizenship and voting is something that developed much later. Really in the 20th century was when the final laws allowing for noncitizens to vote were repealed," said David Bier, director of Immigration Studies at the Cato Institute.
Native-born women had birthright citizenship but couldn't vote. Foreign-born women were automatically naturalized when their husbands were naturalized. Until the 20th century, most single women didn't even try to file their own naturalizations.
The law around citizenship evolved through much of the first three presidential administrations. In 1795, the residency period increased to five years. The more conservative Federalist Party changed that to 14 years in 1798.
"The Federalists in 1798 basically try to shut it all down. They try to do a Trump, more or less. They make it almost impossible to become a US citizen for four years," said Perl-Rosenthal. Congress restored the five-year residency requirement in 1802 under President Thomas Jefferson.
Despite the growing pains, the Naturalization Acts were considered groundbreaking on the world stage.
"The existence of the naturalization law itself was already seen as kind of the most generous in the entire world, the most liberal in the entire world," said Bier. "There were no restrictions based on nationality. There was no restriction based on religion. There was a very short period of residence required. And so it was already kind of built in as one of the most liberal policies in world history to that point when it comes to naturalization."
There was, of course, an enormous restriction based on race.
Black sailors
During the 1780s and 90s, Great Britain siphoned off American sailors, claiming them as British citizens and forcing them into service, or "impressment," upon ships. Frantic letters to custom houses in the U.S. came to nothing, and sailors languished for years on British ships, sometimes serving in their wars.
It wasn't until 1796 that Congress passed the Seaman's Protection Act, letting custom houses issue Seaman's Protection Certificates — effectively citizenship paperwork. Over the next 20 years, the government would issue 100,000 such documents to sailors saying they were citizens of the U.S., including Black mariners.
In the late 1700s, Black Americans faced the challenge of being considered property, British subjects, or citizens. Ultimately their priority was freedom from enslavement — rather than mere citizenship — and many believed military involvement would help free them.
The Continental Army employed 5,000 Black Americans; the British, tens of thousands.
"Free African Americans were basically stateless until the 14th Amendment," said Law. Some northeastern states claimed free Black men as citizens, but the federal government did not.
"African Americans petitioned the U.S. government, pointing to their military service as arguing, 'We deserve to be citizens,' pointing to their birth in the United States, made an argument early-on that they are citizens of the United States. There are definitely many petitions, including from enslaved people who said, we had no consent to our enslavement. We deserve full citizenship just like everybody else," said Law.
The one place where Black men were able to claim citizenship, eventually, was at sea.
In 1780, John Thomson was born free in Salem, Massachusetts, a bustling port. When he was 14, he signed a six-year apprenticeship contract with Captain Robert Emery on the ship Diana.
Documents from the Henry Ford Collection show Thomson's birth and description as "negro, born free."
Years after his service ended, Thomson applied for a Seamen's Protection Certificate for the Port of Philadelphia in 1809.
From 1796 to 1802 alone, Massachusetts issued 13,132, the most of any state. The sailor debacle endured — and sparked the War of 1812 with Great Britain.
Present day naturalization
In 2026, the most common way to become a U.S. citizen is to first become green card holder for at least five years; demonstrate an attachment to the "principles and ideals of the US constitution;" speak, read and write basic English; know the fundamentals of US history and government; and take an oath of allegiance.
People can become U.S. citizens once they're green card holders in less time if they're married to a U.S. citizen, are asylee or refugees, or are part of the U.S. military.
Guilmer Peralta, 19, came to the U.S. as an 11-year-old from the Dominican Republic. He is a green card holder who works at Boston Logan International Airport. Peralta applied for naturalization at a Citizenship Day in Boston in May.
His stepdad, who became a U.S. citizen, lived in Massachusetts for over 20 years. His parents went through the green card process for him when he was a minor.
"Citizenship is something special because obviously it's not granted. It's not something like, you can just do. It's something I feel you earn."
The annual Citizenship Day run by the City of Boston and nonprofit Project Citizenship had fewer people apply this year, according to Gail Breslow, executive director of the organization. This was due to immigration restrictions, including limiting application processing for immigrants from many majority Black and brown countries.
Breslow sees naturalization as a way for immigrants to formally integrate and dedicate themselves to a society that welcomes them. Her own Jewish grandparents fled the pogroms in Odessa in the early 1900s. Another grandparent fled Poland at age 16.
"That is not unlike the stories that many people are telling today, whether they're from Haiti or other countries that are difficult places for people to live," she said. "We are a nation of immigrants, and most of us came here either ourselves or were the descendants of immigrants," she said.
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