Then (left): 1st Division grade school pupils on a field trip in front of the gate to the Henderson Castle, ca. 1899.
Now (right): Still recognizable, though altered, the wall surrounding the Henderson Castle is all that remains of the former estate.
The DC Public Library Commons contains the following information and image of the estate:
Built in 1888 for Senator John Brooks Henderson, the castle stood at the intersection of Florida Avenue and 16th Street, NW (northwest corner). Henderson was a skilled politician and was the man who drafted the Thirteenth Amendment to the Constitution. In 1949 the house was razed, with only the great stone entrance gate posts having survived the wrecking ball.