Complex sentence: In early 1979, the company left its home market of Philadelphia, where the firm was headquartered, closing its more than 50 stores in the area, even though it was the second largest chain in greater Philadelphia in terms of market share.
Split into simpler sentences: In early 1979, the company left their home market of Philadelphia, where the firm was headquartered. The company closed more than 50 stores in the area, even though they were the second-largest chain in greater Philadelphia in terms of market share.