This is apparently a film of the "Avenue of Patriots," one of the several walkways leading to the Perisphere.

It seems to have been a display of many American revolutionary/historical flags, which would naturally include at least one "snake"/"Don't tread on me" flag.

Here's another photo of this array of flags that shows the New England "Appeal to Heaven" flag on the right: http://footage.framepool.com/shotimg/793639081-trylon-perisfere-opening-ceremony-world's-fair.jpg

And another, this one in color (showing that the "snake" flag is white): http://www.billcotter.com/misc/1939nywf/ave-patriots-after.jpg

And the "triangular" Liberty flag (on which you can also see the South Carolina crescent) is, I think actually rectangular; the flags are huge and heavy and there is little wind, so some of them are caught/wrapped on the flagpoles in odd ways.