If the OP really wants to know, I think he could contact someone in government in each of those towns, find out whom is the parade organizer, and ask that person if they know the individual.  The town in Iowa says around 300... I would expect everyone knows everyone in a small town like that..... and if he participated in the parades on a yearly basis, that would more likely - in my mind - that the parade organizer who know who the guy is.

The other thing we don't know..... how old is the picture?  Has the guy passed on already? In that case, it is possible one might have to ask an "old-timer" in town to find out who the guy is.  

It would take a little legwork, but I think it is doable, if someone wants to put in the legwork.