Complex sentence: The professional American football team now known as the Arizona Cardinals was originally called the Chicago Cardinals, and began as an amateur Chicago-based athletic club team named the Morgan Athletic Club, which was founded by Chicago painter/builder Chris O'Brien in 1898.
Split into simpler sentences: The professional American football team now known as the Arizona Cardinals was originally called the Chicago Cardinals. The team traces its history to an amateur Chicago-based athletic club team named the Morgan Athletic Club, which was founded by Chicago painter/builder Chris O'Brien in 1898.