The label says Harzfelds which I guess is a dept store. There is a paper type label in the dress that has no markings left... and the harzfelds label.
https://en.wikipedia.org/wiki/Harzfeld's It looks like Harzfeld's was a Kansas City, Missouri-based department store chain. I believe the dress could be (and might have been) worn for a wedding, but would have been sold as a dress, not a wedding dress especially. At that time, women would have worn such a dress, especially since it is trimmed with the flowers, for another formal event. It would make a great wedding dress though! This is an image from 1971—more or less the same era.
It looks to me like a late 1960s "Prairie Style" dress that could have been worn as a wedding dress. I would not call it a "wedding gown." Edit: I posted at the same time, Maggie!
I wore something very similar but in blue for my cousin's wedding, I was a bridesmaid at his wedding in 1970.
As usual you guys are awesome! I am having so much fun with my adventures into vintage clothes, your label resource is fabulous!! Thank you!!!