This the POW/MIA flag an unofficial symbol in Missouri?

I was driving to St. Louis for a business conference and I noticed that there were a lot of POW/MIA flags on public buildings in Missouri and I saw almost as much of the POW/MIA flags as they are Missouri flags and even United States flags. For anyone living in Missouri, I was wondering why are POW/MIA flags so popular here. I’m from Texas and these flags are rarely seen where I live. I only see them near a few federal buildings and agencies. I just thought this was an interesting culture shock.