Mysterious Archway

Dad ripped off all the trim in the upstairs hallway today in preparation of installing the new floor. When he pulled off the trim from the doorway between the hall and the living room, he found an archway. We always thought the doorway was odd, and it was also very low. Ray, who lived upstairs a year ago had to duck when he walked through it. Why someone would cover up a perfectly fine archway to make a narrow and low doorway is a mystery, especially when there is a matching doorway on the other side of the room.