Religious affiliation is more difficult to categorize than occupation or immigration. Affiliation could change over time, as when some Quakers followed George Keith in 1692 and became Baptists or Anglicans. And it was not always recorded. The Quakers were the only group with surviving early records. If someone does not appear in the Quaker records, does that mean that they were not Quaker, or simply that they were not active in the meeting?

Evidence for religion comes from Quaker meeting records, burial records of non-Friends, wills (for example, those with bequests to other churches). sometimes by association with people of known affiliation, like the Dungan family of Baptists.

Certain assumptions are reasonable. The Swedes were overwhelmingly Lutheran, many attending the church at Wicaco, later Gloria Dei. There were known Anglicans in the province, such as William Markham and George Foreman. There were people whose behavior shows that they were not Friends, like Gilbert Wheeler the unruly innkeeper.

Using available evidence, religious affiliation was classified into Quakers, Lutherans, Unknown, and Other, a category that included Baptists, Anglicans, and the occasional Catholic. As the table shows, the people on the map were predominantly Quaker.

Does this mean that the people in the province were predominately Quaker? The answer is no. There were many people missing from the map who show up in court records, wills, and land records, and many of them were not Friends. Since the Quaker meeting houses were too small to hold the population, even in the early years, it is clear that many people in the province were unchurched.