Frederick Law Olmstead was a Fianna Kinfolk. He and fellow Kinfolk Calvert Vaux designed and built New York City's Central Park from 1858-1861 so that it could be used as a caern. The Sept of the Green was eventually founded, despite actually having been a former Wendigo caern.  He was also instrumental in saving the Sept of the White Water from the Wyrm in the 1800s, and as a result, the Fianna and Uktena have shared the caern ever since. 
For information on the real person, please see Wikipedia:Frederick Law Olmstead.