I know now what unconscious process made me look up the official founding of
the Border Patrol when I saw that tweet, not because I already knew about it,
but because I didn't know about it and wondered why—I've often dipped into the
history of immigration and immigration enforcement on the blog, and you'd
think I would have heard of how the Border Patrol got started.
The main reason I hadn't heard about it, as it turns out, was that it happened
at the same time as everything else, in 1924, during the Coolidge
administration, when they passed the first general immigration law in the form
of the National Origins Act; before that, the Mexican border was essentially
open, Mexican and US citizens going back and forth across the border freely,
unhindered except by customs agents collecting import duties on both sides.