Another quote from wikipedia on the "obliterated" Vandeventer Place:

Vandeventer Place, opened in 1870 and included a house design by H.H. Richardson. Vandeventer Place has been completely obliterated, with the exception of the east gate, which was removed to Forest Park.

These gates are visible today right by the Jewel Box in Forest Park.  They were moved there in 1950.  There's a nice write up of the gates at the St. Louis Patina blog...