Illinois's or Illinois'

Need a little help.
Editing something for a poet laureate and he used "Illinois's." I think it looks horrible, but I want to make sure before I go correcting this guy.
Thoughts?

 

I think either is acceptable for non-newspapers, but I've never seen a newspaper use s's as a possessive.

 

Interestingly, I Googled "Illinois's" and the second hit was from the Washington Post.

 

Strange. Of course, the WaPo has its own style manual. AP style stipulates just an apostrophe after a noun.

 

Ellis is right. They have their own style manual. S'S seems a bit superfluous.
NY and LA Times (and AP) use S'.

 

I agree that s's is superfluous.

But how do you guys feel about x's? Like, say, Podunk High quarterback Harry Cox's first pass was intercepted? Or is it Harry Cox' first pass?

 

Well, the other thing is, a poet laureate is going to perhaps be edited differently than a newspaper story on a basketball recruit.

Ours and AP style is Illinois' -- but honest to god, it probably ought to be how the poet laureate wants it.

 

Old school editing says Illinois's, new school editing says Illinois'.
This has been a topic before and one old rule was that if the S was silent, then you would add the 'S to make to possessive. If the S wasn't silent, then it would be just the apostrophe.
Another old rule is that with proper names you always add the 'S. So it would be Jesus's cross or Bonds's homerun.
Kinda depends on the paper and if they have a style or if they just follow the AP.

 

I've always been told that it's only an apostrophe after an s, x or z.

 

That's what we decided.

 

What I go with.