Accoring to Mark Ambinder of The Atlantic.com:
It wasn't so much that Barack Obama had real fight in him tonight, or that more people attended his rally in front of Independence Hall than any other event since he announced his candidacy. It was the spontaneous demonstration of support that happened when it ended.
5,000 people (at least) had nowhere to go but up Market Street. Obama's charge of the night: "Declare independence!" was with them. They started with the familiar "O-Bam-A." By 7th and Market, they had graduated to "Yes we can!" By 10th and Market, with hundreds streaming in between cars on the road, they were just cheering. At first, a few Philly cops, killjoys, tried to rough the crowd to the sidewalks. It didn't work. The cops retreated to the sidewalks. By the time I ducked into my hotel, a full mile away from Independence Park, the Obama crowd was still marching. (Read the rest of the article.)
Here is video of it: It's amazing, that we can still be so inspired. Just WOW!