No official word went out about the visit but the buzz got going on Twitter.
Flanked by the Secret Service, the First Lady and her daughters went to the heart of the country's history -- Independence Hall. They visited the Liberty Bell, the Betsy Ross House, South Street and the Gayborhood.
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Out-of-towners Michael Cohen and is wife were in Philly over the weekend and snapped a few photographs by the Liberty Bell. "We had to reschedule our tour due to the First Lady's trip," said Michael. "But it was worth it."
We'd love to post any pictures you snapped of the First Lady and her daughters during their surprise visit. Just email 'em!