Chicagoist has the rest of the info. Essentials:

When: Saturday, July 19 
Tickets: this Friday @ 5 p.m. via Live Nation/Saturday @ 10 a.m. via Ticketbastard (zzing!)
Venue: First Midwest Bank Amphitheatre in Tinley Park
Line-up: FLIPPIN’ INCREDIBLE!!!!
The Pharcyde, A Tribe Called Quest, Nas, Mos Def, Method Man & Red Man, De La Soul, Rakim, Immortal Technique, Dead Prez, Murs, Wale, Jay Electonica, Kidz In The Hall…