The ISP was the first agency to issue autos and also the 9mm. Salt Lake City PD was 2nd. A lot of agencies allowed their officers to carry autos but no agency was issuing autos prior to 1968.
If was first adopted in late 1967 with the first ones being issued in 1968. We carried S&W autos until 2000 when we transitioned to Glock. Not that we didn't want to stay with S&W but when Glock shot a price of 1/2 what S&W bid then there was no choice but go Glock.
Many of the changes to the S&W auto and 9mm ammo was a direct result of suggestions made by our range officers.
The 39-nothing pictured below was one of the first year issues. I carried it until 1981 when we went to 439. All the 39-nothings were stamped with "ILL S.P." and an inventory number. Some of the 39-2 models were so stamped. The number is not the Troop's ID number as some places have reported. Back then the state of IL purchasing rules required every piece of state equipment valued over $100 to have an inventory number. Serial numbers weren't good enough. Even squad cars had to have an inventory number. That law was later changed if the manufacturer had a unique and recognized system for assigning serial numbers.
We were allowed to buy our issued guns when we went to new models. It's got a super slick trigger from our range guys tuning it and from having a ton of ammo run thru it. With a good handload it will cut the X ring all day long on a 25 yd bullseye target.
RE the FBI and the .38 Super. The field offices still had .38 Supers in the vaults into the late 70s. Hoover was not a fan of autos. He considered them to be gangster's guns. The .38 Supers were for issue to agents who would be going undercover and needed a 'gangster gun' to carry instead of the issued Colt or S&W revolver.