Depends on your timespan. In the modern era only failed states that can’t actually secure their own borders have unfettered immigration; but it’s pretty rare for people to want to go into such countries.

Scroll back a few centuries, and what we’d consider to be “open borders” was much more the norm.

Then again, a few centuries before that and the vast majority of residents in Europe couldn’t legally leave the land that they were on, forget the concept of immigration. Leaving town could make you an outlaw, let alone your country.

That's still true in some places today.

The United States before 1924 for one. Passports and travel documents didn't really exist at all until Napoleonic-ish times and weren't widespread until about WWI.

I personally feel that defining "citizen" in any other way than "people who are currently living here" is a form of apartheid and antithetical to our constitution.

Part of why immigration law is so confusing and contradictory is that the framers of the Constitution had no concept of someone living in a country (with intent to stay) and not being a citizen. Even slaves and women were considered citizens.

They definitely did have an idea of people living here who were not citizens. Thus the Naturalization Act of 1790.

Or in 1882 when Congress passed the Chinese Exclusion Act.

Svalbard might fit the bill. See https://en.wikipedia.org/wiki/Visa_policy_of_Svalbard