Many Americans get the Pilgrims and the Puritans mixed up. Common thinking is: They were both groups of English religious reformers. They both landed in modern-day Massachusetts. And they were both stuffy sourpusses who wore black hats, squared collars and buckled shoes, right?

Well, maybe not the buckles.

To understand the biggest differences between the Pilgrims and the Puritans, one has to go back to the Protestant Reformation, which swept across Europe after Martin Luther (supposedly) nailed his “95 Theses” to the church door in 1517.

Thanks to the printing press, non-clergy had access to the Bible in their native languages for the first time. They began to question why the Roman Catholic worship services were so different than those of the primitive Christian church.

The Reformation was slower to arrive to the British Isles, but England had its own split from the Roman Catholic church in 1534 when King Henry VIII wanted a divorce and the Pope wouldn’t grant it. The newly created Church of England was similar to Catholicism in every way, except instead of the Pope carrying divine authority, it was the British Crown.

Every British citizen was expected to attend the Church of England, and those who didn’t were punished by the state. One group of farmers in Northern England, known disparagingly as the Separatists, began to worship in secret, knowing full well that it was treasonous.

“Once they decided that the only way they could be true to their conscience was to leave the established church and secretly worship, they were hunted and persecuted, and many of them faced the loss of their homes and the loss of their livelihood,” says Donna Curtin, executive director of the Pilgrim Hall Museum in Plymouth, Massachusetts. “When it became impossible for them to continue in this way, they began to seek another place to live.”

The Separatists first fled to the Netherlands, a wealthy maritime superpower that was far more religiously diverse and tolerant. But while life in Holland was peaceful, it wasn’t English, and the Separatists feared that their children were losing their native culture. They decided that the only way to live as true English Christians was to separate even further and establish their own colony in the New World.

Not all of the Separatists could make the cross-Atlantic journey, including their spiritual leader, Reverend John Robinson. Writing years later in Of Plymouth Plantation, William Bradford recounted the tearful farewell at the docks in Delftshaven, where a ship would take the Separatists to meet the Mayflower in London.

“So they left that goodly and pleasant city which had been their resting place near twelve years; but they knew they were pilgrims, and looked not much on those things, but lift up their eyes to the heavens, their dearest country, and quieted their spirits.”

Curtin points out that Bradford didn’t name his community “Pilgrims,” and wouldn’t have heard the term in his lifetime. The first usage of capital-P “Pilgrim” appeared around 1800, when a group of citizens in Plymouth proposed the creation of a Pilgrim Society to organize the annual celebration of the founding of the Plymouth Colony in 1620. Before 1800, the Separatists who landed at Plymouth Rock were known as the “first-comers” or “forefathers.”

The Pilgrims, led by Bradford, arrived in New England in December. Roughly half of the 102 passengers on the Mayflower died that first winter from starvation, exposure and disease. With the help of the native Wampanoag people, the Pilgrims learned to fish and farm their new lands, resulting in the famous feast of Thanksgiving attended by natives and new arrivals in 1621.

So who, then, were the Puritans? While the Separatists believed that the only way to live according to Biblical precepts was to leave the Church of England entirely, the Puritans thought they could reform the church from within. Sometimes called non-separating Puritans, this less radical group shared a lot in common with the Separatists, particularly a form of worship and self-organization called “the congregational way.”

In a congregational church, there is no prayer book, no formal creeds or belief statements, and the head of the church isn’t a Pope or the King, but Jesus Christ as revealed in the scriptures. Sabbath worship doesn’t include sermons and preaching, but extemporaneous “testifying” by the Holy Spirit. As an organizing principle, congregational churches are bound together by a “covenant” and make decisions democratically, including the selection of religious leaders.

The biggest difference between the Separatists and the Puritans is that the Puritans believed they could live out the congregational way in their local churches without abandoning the larger Church of England.

“The Puritans said, ‘It’s completely acceptable that this ecclesiastical structure is above us, but we’re going to operate as a congregation in this biblical way,’” says Vicki Oman, associate director of group participation and learning at the historic Plimouth Plantation. “The Separatists said, ‘That’s baloney. We have to completely separate ourselves and have this congregational community separate from the state church.’”

This theological split between Separatists and non-separating Puritans had lasting consequences.

“Separatists end up on the outside of society,” says Oman. “Even if they’re educated, they end up with low-paying jobs. They leave for places like the Netherlands, where they’re also not financially successful. Meanwhile, the Puritans stay wealthy.”

The Puritans ultimately decided to journey to the New World, too, but not for the same reasons as the Separatists. The Puritans, who already had some money, saw a favorable investment opportunity by owning land in America. And somewhat paradoxically, the Puritans also believed that by being far away from England, they could create the ideal English church.

“[The Puritan leader] John Winthrop talks about creating a church that will be a light to the nations,” says Oman. “The Pilgrims never really expressed that desire.”

When the Puritans settled the Massachusetts Bay Colony in 1630, they arrived in 17 ships carrying more than 1,000 passengers. They came with money and resources and divinely ordained arrogance. Just 10 years later, the Massachusetts Bay Colony was a Puritan stronghold of 20,000, while humble Plymouth was home to just 2,600 Pilgrims. Plymouth was fully swallowed up by Mass Bay just a few decades later.

Because the Pilgrims and the Puritans share a similar backstory, their legacies often got blurred in the minds of later generations of Americans, and not always accidentally. Writing in 1820, Daniel Webster used the Pilgrims as nostalgic symbols of Manifest Destiny, which was more of a Puritan thing:

“Two thousand miles westward from the rock where their fathers landed, may now be found the sons of the Pilgrims ... [cherishing the blessings] of wise institutions, of liberty, and religion."

Sarah Crabtree, a historian at San Francisco State University, admits that she gets frustrated by the “slippage” between the Pilgrims and the Puritans.

“It contributes to the myth that ‘the first Thanksgiving’ and ‘religious freedom’ are part and parcel of America’s origin story,” writes Crabtree in an email. “The Puritans and their ‘City on a Hill’ explicitly rejected religious freedom and never attempted to adopt the Pilgrims’ initial, fleeting cooperation with American Indian peoples.”

And those black hats and buckled shoes? That popular imagery of the Pilgrims was dreamed up in the late 19th- and early 20th century. Oman says that buckles were around in the 17th century, but weren’t Pilgrim fashion, and black dye would have been too expensive for the humble settlers. Only the wealthier Puritans may have worn black hats. Pilgrim clothing was likely very colorful, full of blues, greens and oranges.

“A lot of our mythology about the Pilgrims comes out of the early 20th century, when Americans were once again recreating their identity at a moment of great cultural upheaval,” says Curtin. “America was changing with the rise of manufacturing and the rise of immigration, when many new people were coming in to become Americans.”