In the Middle Ages, much of the population was illiterate, so windows such as these were used to tell stories.
The nave windows, starting on the southwestern side with the Nativity window, follow the story of Christ's life and teachings by illustrating many of the parables he used. They end on the southeastern side with the resurrected Christ giving the Great Commission, instructing his disciples to spread the Word of God to all the world.
The clerestory windows depict the disciples of Christ on the west side and Old Testament prophets on the east side.
The choir window shows Union's original and present building alongside depictions of Martin Luther.
The baptistery window shoes scenes of Christ being baptized by John and scenes of Christ with children.
The altar window shows many scenes including the Garden of Eden, the Crucifixion of Christ and Matthew, Mark, Luke and John, the four Gospel writers.