Complex sentence: He moved to a Walgreens store in downtown Chicago after his graduation where he became a chocolate syrup maker up until 1949 when he started delivering Walgreens products as a truck driver throughout suburban Chicago.
Split into simpler sentences: He moved to a Walgreens store in downtown Chicago after his graduation where he became a chocolate syrup maker. He kept the position until 1949 when he started delivering Walgreens products as a truck driver throughout suburban Chicago.