I've seen lots of people claim that the U.S. had open borders before the 1920s (or before the Chinese Exclusion Act). It's just not true.

Read "Expelling the Poor" for a history of state-level immigration restriction in the 1800s.https://t.co/DZeGL83uxN

— Noah Smith 🐇 (@Noahpinion) December 6, 2019

I thought this bit of “open borders” propaganda was probably wrong, and meant to research it, but never got around to it. Now I have my answer.