To be picky; the WPR '72 meet was the USOC - the 3rd. And the first sanctioned by the USOF at the 1st AM earlier in the year. The re-run MD will let the CPs stay out for the next 5 days (thru Thursday Oct 18). See end of AP thread NEOC 40!
NAOCs started in 1973 with Ottawa OC hosting it in Gatineau Park, Que, on Sept 1-2.