The Founder's Oak is a local Greenpoint landmark designating the spot where Zebediah Peters founded the town on April 17, 1884. It's also used as the starting spot for a phony treasure map followed by Spanky McFarland, Buckwheat Thomas, Mickey Gubitosi and Froggy Laughlin. It's possibly part of Media Park from Bouncing Babies.
The inscription visible in the film reads "Zebediah Peters and his party met, and decided on this site for the town of Greenpoint." According to theluckycorner.com, a publicity still reveals that the top of the plaque reads "Founder's Oak - Here on April 17, 1884."