I finally got to this episode recently. First let me say I love both Tower Topics and The Attractions Group podcasts. Always interesting stuff...
That house has fascinated me for some reason. At one point not too long ago I went down the rabbit hole of seeing what historical information might be available about the property online and learned quite a few things. None of that is super exciting, but perhaps a few details might be worth sharing...
Based on various property records, I believe the house was built sometime between 1954 and 1956.
I can't speak for or against the accuracy of the supposed agreement to not tear it down, but FWIW it was actually one of three houses side by side all along what was the east side of Columbia Rd that Kings Island left standing, and apparently used in some capacity, for many years. Each property had different owners prior to Taft purchasing each of them separately in early 1970. All 3 houses were still standing at least until 1986. 2 of the three until at least 1993. By 1997 only the one in the fort remained.
Hopefully I'm attaching these images correctly...
The first one is snip from a survey from 1984 showing each of the original property boundaries of the three houses KI kept around. The house in the fort is the southern most of the three plots in the red circle.
The other images below are all snippets cropped from aerial photos made available online by the Ohio Department of Transportation. In each one the "fort house" is circled in red.
Here is 1956. Fort house is recently built. The middle of the 3 houses is being built. No sign of the northern house yet. The old farm house further north in this photo would not survive the park opening.
Here is 1957. The middle house is now complete. The fort house has added a pond. Still no sign of the northern most house.
Here is 1964. The northern most of the 3 houses the park would keep is now present. The middle house has added a garage or large shed.
Here is 1970, the year Taft purchased each property. All 3 houses were purchased on different dates in Jan and Feb of that year. The northern most house looks to have added an addition to back since the 1964 photo. This one is at an angle that gives a reasonable idea of what the housed looked like before the park owned them. Also of note the old farm house further to the north is still standing at this point.
Here is 1972. The park is open now. All 3 homes are still standing. The older farm house that was further north is gone. This photo shows what Don described in the episode that the train did not originally come particularly close to the house.
Here is 1974. Cars parked at all 3 houses. This one is angled to show a bit of the front of the houses.
Here is 1975. Another one showing a decent look at the houses.
Here is 1986. All 3 houses still standing and appear to still be used in come capacity.
Here is 1993. The middle house is now gone. It would have been in the way of the re-route of the train for the water park. The fort is now build around the southern house. The northern house is still standing though.
Here is 1997. The northern most house is now gone, only the southern one inside the fort survived this long.