Philadelphia is kind of an important city in U.S. history, what with the whole Declaration of Independence signing and the Liberty Bell and whatnot. (Cheesesteaks didn't come until later, although in our humble Shmoopinion the cheesesteak is as important as anything Ben Franklin dreamed up.)
So it was already on the map before Rocky, but Rocky made it a tourist destination for a new reason: to run up the stairs of the Philadelphia Museum of Art. Now known as the Rocky steps, tourists can burn off hundreds of Philly cheesesteak calories in their dash to the stop, where you can now literally stand in Rocky's footsteps.
But what makes this scene so iconic? It's because Rocky is so dang inspirational, and a lot of that has to do with the setting. Rocky is struggling in Philadelphia. We don't see fancy locations. We see back alleys, rough neighborhoods, sweaty gyms, and raggedy apartments. When Rocky says, "It stinks in here, huh?" he is both saying that he needs Febreze, and saying that his life situation stinks. He loves his city, he just wants to live in better parts of it, like many people do.
Also, the time Rocky is set is just as critical as its location. We begin on November 25, and see three major holidays in Rocky—Thanksgiving, Christmas, and New Year's Day 1976.
Although they never use the word "bicentennial," that's why 1976 is such a big deal for Apollo and his desire for a patriotic narrative. July 4, 1976 marked the 200th anniversary of the U.S. Declaration of Independence—another reason for having the big fight in Philly, and for Apollo to pick an opponent who calls the City of Brotherly Love home. (Apollo's patriotic duds make more sense when you realize the significance of the year, right?)