Then I think most of us are using the popular term which meant there was only
one station on the frequency. Not even a daytimer shared it.


U.S. Class I-A clears a 640-670, 700, 720, 750-780 820-840, 870-890,
1020-1040, 1100, 1120, 1160, 1180, 1200-1210

Canadian Class I-A clears: 540 (first), 690, 740, 860, 990, 1010, 1580

Mexican Class I-A clears: 540 (second), 730, 800, 900, 1050, 1220, 1570

I'm having trouble thinking of a single U.S., Canadian or Mexican Class I-A
clear channel which did not have at least one co-channel daytimer somewhere in
the U.S.

And, remember that stations in the U.S. territories (and former territories,
now states) were allowed to operate on U.S. Class I-A clears many decades
before "Rio" caused all clears to be completely broken down.