...which allowed Illinois Lottery machines to be placed at the airports. Very odd time..
That was also due to the takeover of Chicago expressway coverage by the ISP around the time as well. I think the merger of Districts 3 & 4 followed that.
Many years ago (1970's) they attempted a merger of Districts 3 & 4 as well, making it "District 17" for a short period. They temporarily housed "State Police Des Plaines" at the old 477 S. River Road facility then used by DCI and then the ICC police. AFAIK only the District Commanders offices moved to River Road. They never closed the two separate posts (Harlem & Irving and Crestwood) and shortly thereafter reverted back to separate Districts 3 and 4. The details are a bit fuzzy from the passing of time but ISTR that they never changed radio numbers or made any substantive changes.
Until the 1970's (some of these lasted into the 80's) the ISP had several "Sub-Posts", basically a remote office of the main post with a lessor rank in command, answering to the main post. They usually had their own dispatcher, but I think they remained on the same freq as the main post in many if not all of them. Eventually all of the Sub-Posts gained full Post status and moved onto their own channels. It appears that this reorganization might reverse this and re-merge some of the old Sub Posts into their former parents.
The Sub-Posts I can recall are:
Rockford (Pecotonica), was 1A, now 16
LaSalle was 5A (Peru) and is now 17
Litchfield was 11A, and is now 18
Carmi was 12A and is now 19. (Was 12A located at Fairfield before Carmi?)
Pittsfield was 14A and is now 20.
Ashkum was 6A and is now 21
Ullin was 13A at Cairo, and is now 22. 13A was the last remaining ISP Sub Post and moved up to Ullin in the mid 1980's when it became 22.