We have an old tenement (possibly Old Law, possibly pre-Old-Law) on the left, with the white-painted street facade, and a 1960s or 70s apartment house on the right. The apartment house has a cellar garage, and the ramp from the street down to the garage is located on the lot line, next to the tenement. So whatever was next to the tenement was demolished when the apartment house was built or before.
The ghost on the tenement’s side wall threw me for a bit. There are several pieces to it: the filled-in lot-line windows on the 2nd, 3rd, 4th, and 5th floors; the remnants of a chimney just to the left of the filled-in windows; the traces of a front facade for the full height of the building where the side wall meets the front facade; prominent traces of framing at the 2nd-floor level; and faint traces of framing at the 4th, 5th, and roof levels. The wall is coated with stucco or some kind of waterproofing, which blurs the edges of the ghosts a bit.
The windows obvious imply that the lot-line wall was not facing a building taller than one story at some point. The strong traces of framing at the second floor level agree with that. But the traces of framing higher up and the traces of a front facade suggest that there was once a building the same height as this one. Tenements were often built in groups, much like rowhouses, so it wouldn’t be surprising if there had been an identical building next door.
My theory is that there was an identical tenement there, which at some point was cut down to one story tall. When that happened, windows were opened up in the side wall of the white-front tenement to take advantage of the extra air. Unfortunately, this may be hard to prove. The white-front building is 239 East 80th Street and, sure enough, it had a twin at 241 East, where the garage ramp now is. Using the readily-available fire insurance maps, I know that as late as 1955, both buildings were still five stories tall. In 1980, when the second tax photo was taken, the 241 building was already gone. Given that my theory can neither be proven nor disproven, I’ll declare victory and move on.