Pennsylvania became the second state to ratify the US constitution.
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The first music store in America was opened in Philadelphia by Michael Hillegas.
A nuclear disaster occurred at Three Mile Island in Pennsylvania, US.
The Marianna Coal Mine in Pennsylvania exploded and killed 154 men.
The famous Liberty Bell arrived in Philadelphia, US.
Polio vaccines were given to the first group of children in the US at Arsenal Elementary School in Pittsburgh, Pennsylvania.
