Simplify the following text for a Grade 6 native English-speaking person.
Original: The Free Hanseatic City of Bremen ( German : Freie Hansestadt Bremen , ) is the smallest of Germany 's 16 states .
Simplified: The official name is `` Freie Hansestadt Bremen '' . This is because Bremen used to be in the Hanseatic League which was a group of cities which did a lot of trading .