IIRC, the Illinois Staties were among the early adopters, beginning I believe with the 39.
That’s my understanding, as well. Because of the ISP’s apparent satisfaction with 39s, the CHP was considering their adoption in the late 1960s, as I was going through the Academy. Didn’t happen, though. My Academy class was the first to be issued guns, the Colt Officers Model Match (lots of problems). The very next class, and many thereafter, were issued the S&W Model 14 (very good), followed by stainless steel Model 67s and 68s. The CHP’s first semi-auto pistol was the S&W 4006, first issued more than a decade after I’d left.