Simplify the following text for a Grade 9 native English-speaking person.
Original: He designed the German Empire in 1871 , becoming its first Chancellor and dominating its affairs until he was removed by Wilhelm II in 1890 .
Simplified: As Prime Minister of Prussia from 1862 to 1890 , he was mainly responsible for unifying the many independent German countries and founding the German Empire in 1871 . He became the first chancellor of the new Empire .