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NAtower NA Tower, Martinsburg, West Virginia
This "tower" is not a tower in the traditional sense as it is just one story tall.  It was however an interlocking tower from the start to the end of the 20th century.  Martinsburg opened in either 1898 or 1900 and closed in 2003.  It remains standing, but boarded up to this day.

Below is a shot of the real tower around 1975 or so.