Hard hats can be found as helmets throughout history.
Soldiers have adapted helmets for head protection from the beginning of military record keeping.
The helmets developed in WWI were made out of metal and widely used by all soldiers.
After the war, these helmets were adapted for worker safety on construction sties and in manufacturing settings.
The industrial hard hats were initially made from metal, then they evolved to fiberglass.
Hardened reinforced plastic hard hats are the most common types of hard hats used today.