Final answer:
The sentence "When I was a young girl, my family lived in Pennsylvania" is a complex sentence that contains one independent clause and one subordinate clause.
Step-by-step explanation:
The sentence "When I was a young girl, my family lived in Pennsylvania" is a complex sentence. It contains one independent clause (main clause) and one subordinate clause. The independent clause is "my family lived in Pennsylvania" and the subordinate clause is "When I was a young girl". The independent clause can stand alone as a sentence, but the subordinate clause cannot.