In a Philadelphia victory speech, Clinton told supporters that while some called for her to drop out of the race, the American people "deserve a president who doesn't quit."
The primary battle now turns to North Carolina and Indiana, which vote in two weeks.
Obama spoke in Evansville, Indiana, last night. He noted the nasty tone of the Pennsylvania contest, saying the "distractions" and "bickering" trivialize the issues in the campaign.
Obama won at least 57 delegates in Pennsylvania and retains the overall delegate lead, though Clinton has narrowed the gap.