Illinois's or Illinois'

Agreed. ... Illinois'

 

As someone whose last name ends in "z" (how's that for subtle self-outing?), I've seen the possessive used without the "s." It looks odd. Same for "x."

But there should be no "s's".

 

How about an acronym for a school name that ends in S? Say, for example, there's a school called United School in your coverage area, and while they're mostly called just 'United,' they are sometimes also called 'US.' Would the possessive be US's or US'?

 

How about adding an "s" to your pen name, shotglass?

 

Nope. It's a no-go, says shotglass' agent.

 

Now that we have that settled, what about the possessive of A's?

The A's' strong farm system?

(Of course no one would ever print that, but how would you differentiate the possessive form from the regular old contraction?)

I've also wondered the same thing about McDonald's ... how do you make that possessive when it already is?

 

The strong farm system of the A's.

 

Oakland's strong farm system.