No self respecting Hiawatha should ever hang out in a scrapyard!!
Looks a lot like my '40 Gamble's Hiawatha. Can you post a serial number, that may help narrow a year of manufacture down a bit. It looks like a Cleveland Welding frame, but I'm by no means an expert.
Should be something stamped on the underside of the bottom bracket. Sometimes, you will need to remove the paint to find it, but if it's a Cleveland Welding or Shelby frame, it will be there.