User blog comment:Mr. Youtube/Columbia and Rapture/@comment-158.130.223.195-20130426190558

Rapture and Columbia are supposed to be parallels of each other in the two main alternate realities. In the reality in which Booker accepts Baptism and becomes Comstock, Columbia is built, and Rapture never comes to be. However, in the reality in which Booker denies Baptism, he never becomes Comstock, and therefore Columbia is never built. Rapture is instead theorized and created by Andrew Ryan.