A group of young people enjoy an outing at Portage Bridge. According to the label, the group is made up of young people from Brooksgrove and the Ridge along with the proper chaperons. Nearby is the dancing pavilion owned by the Erie Railroad. The popular structure was located in a grove just north of the east end of the bridge.
The label suggests that the picnic took place "about 1920", but it had to be earlier, likely between 1916 and the summer of 1918. We know this because Helen Piper, seen on the far right, died of the Spanish Flu in October 1918.
See http://www.letchworthparkhistory.com/eriestationmap.html for a map showing the location of the dancing pavilion and railroad's park.