Complex sentence: When opened, it was marketed as being the highest high speed six pack in North America, a title it retained until the Kensho SuperChair at Breckenridge Ski Resort was built in 2013.
Split into simpler sentences: When opened, it was marketed as being the highest high speed six pack in North America. It retained this title until the construction of the Kensho SuperChair at Breckenridge Ski Resort in 2013.