Complex sentence: Bonwit Teller would change ownership several times throughout the 1970s and 1980s until 1989, when its parent company at the time filed for bankruptcy protection, liquidating most of the company in 1990.
Split into simpler sentences: Bonwit Teller would change ownership several times throughout the 1970s and 1980s. In 1989, its parent company at the time filed for bankruptcy protection, liquidating most of the company in 1990.