Did you ever notice that Milwaukee Summerfest north gate is quite different from the other two gates? When you enter Summerfest from the north, it's hard not to notice the Milwaukee Art Museum as it's in full view. There is grass, and a view of Lake Michigan when you come in from the north gate.
Summerfest's center gate is where you will find the most people, because the ticket booths are right there. The south entrance can be crowded too. That's where the Marcus Amp. people arrive.
The Summerfest North gate entrance puts you right by the rock stage too. It's also where you can grab the sky glider and head south over the top of the crowd. No matter where you enter, you will have a great time.