Determining the identity of the 21 men in this image involved reversing the flag, in order to read the inscribed lettering. The words "Alfred" and "Camp 16" was easy enough to read, and this seemed to match that of the Col. Alfred F. Holt Camp, No. 16, of Lyndeborough, New Hampshire. The men's caps also had "16" and the letters S and V, showing they were Sons of Veterans.
None of the buildings exist today. Below is a circa 1910 postcard of Railroad Square that shows most of the buildings still standing, except for the smaller livery/stable, replaced by the Stearns Building ca 1902.The buildings circled can be seen in the 1889 photo.