So, this morning I took a good look at the catalog entry for Illinois, Cook County, Marriage Records, 1920-1950.
Scrolling down quickly, looking for camera icons, it looked like all the licenses from 1920 to 1941 were accessible and that a few after that date had also been put online. But, taking a closer look, I realized that the available "later" records are actually from 1941.
Here's what's up:
The "film" notes begin with descriptions that include series, license numbers, and years, and--really important--the entries are sorted by that information. (See images example below.)
It works great for series 1 which covers 1920 to part of 1923.
Then the fun begins.
Series 2-1, 2-10, and 2-100 sort before 2-1000 which means they're out of place. Then the order is consistent until it reaches 2-1009 where it jumps to 2-101, putting a 1924 group in the middle of 1936. Then the pattern resumes.
So, why is this a big deal?
Well, actually, it's not a big deal. But, if you're searching for a license and it looks like there's a gap where it should be, it doesn't mean it wasn't digitized. It just means that you need to look for it in another place. One easy way to do that is to use Ctrl-F or Command-F ("F" is for "find") to quickly search for a year.
Knowing what's up, I can feel confident in making a mental note that Cook County marriage licenses, 1920-1941, are available on FamilySearch and can be accessed from a Family History Center or an affiliate library.