Where to mail I-485 etc. for a K1 visa holder?

[confusing 5]

I'm sorry for this seemingly obvious question... but I've searched here for a direct answer, and the USCIS site seems to be going up and down today.

I am filing all of our AOS papers for a K1 visa holder. I am located in South Carolina, and from what I read all AOS docs go to the Chicago Lockbox... but I can't seem to find the exact address I need to send them to.

"Note: When filing for Adjustment of Status K1 and K3 Visa holders are now required to submit their paperwork to the National Address (Chicago Lockbox) instead of at their local CIS office"

That's from the guide here.

Could someone please help me out?

[confusing 5]

I think this is it:

For USPS deliveries:

USCIS

P.O. Box 805887

Chicago, IL 60680-4120

Can I get a return receipt/delivery conformation if mailed to a P.O. Box?

For Courier/Express Deliveries:

USCIS

Attn: AOS

131 South Dearborn - 3rd floor

Chicago, IL 60603-5520