"Do you hear me Philly? It is time to do something different. It is time for change," said singer Mary J. Blige.
Blige, Jay-Z, and Sean "Diddy" Combs, some of the biggest names on the hip-hop scene, have been travelling the country encouraging people to get out and vote.
Barack Obama needs a big turnout in Philadelphia to win Pennsylvania.
"John McCain desperately needs Philadelphia, but you can tell him 'You cannot have Pennsylvania,'" said Jay-Z.
But McCain does have a chance to win Pennsylvania's 21 electoral votes, if voter turnout is low in urban centers like Philadelphia.
The star-studded cast of this block rally is determined to make sure that doesn't happen.
They're working hard to get new voters to the polls.
"It's about the youth vote, it's about the long lines and getting them prepared. The youth vote will decide the next president of the United States," said Sean "Diddy" Combs. "They said we wouldn't come out, they said we wouldn't vote, but we're going to shock the world tomorrow."
An unexpected guest also made an appearance. Jay Z's wife, Beyonce Knowles helped work the crowd.
"I'm so proud of our young people, this is so huge," said Beyonce. "It's all about diversity and unity and Obama for change!"
And that is the mantra that has energized this crowd: Change.
"I think it's important that we all get out and vote. We can't let another Republican get another turn, we've got to get a Democrat in there," said Raz Williams of North Philadelphia.
Change is coming one way or the other, Obama or McCain. Was today's big name rally enough to blunt McCain's all out push in Pennsylvania? We'll see on Tuesday.