Maybe one of the many FDR new deal programs?? I would think the numbers on the tents were there so one would know what tent they belonged in and how the mail could be routed to the right individual in a man camp? That fella in the back of the tent is holding something upright and I can't tell what that is, plus they all seem to have one kind of shirt? Unless someone wrote some info on the back, this will be a tough one to say for sure what all is going on here..It could maybe be the Corps of Engineers? The guy in the tent and the fella on the far left have the same type of hats that look like early 19th century military style hats maybe??.