They were wanding people coming in to the stadium. I am too lazy to look it up but likely this is some sort of NFL rule. They started doing this on the last regular season home game and it almost started riots (see here). This is the line before game time (I took it from inside the stadium, through the fence - this is the north side by the museum); we packed up our tailgate early to avoid the line and got in just fine about a half hour before kickoff but a lot of people who waited were stuck in this line or ones elsewhere around the stadium and they probably got in late.
Can't believe I'm saying this but the parking situation prior to the start of the tailgate wasn't as idiotic as usual. Typically they "roust" you and don't let you idle in one spot before they open the Adler lot at 8am. This time they let us sit and we were one of the first people in line. We asked if we could park by the grass to set up our tent and the guy said something along the line of
I take care of you, you take care of meHe did give us a great spot (although the "hated jukebox" parked near us, later) so I went up to him and gave him a ten spot surreptitiously.
That's the "Chicago Way".