Most early cars did not have a windshield, they were manufactured with an open air design. Drivers wore goggles to protect their eyes from the elements. The windshield became popular because it was an improved way to protect yourself and your passengers from wind and debris. The first windshields were made out of glass. Instead of helping people, the shattering glass on impact would actually cause more injuries, then the windshield was meant to protect. That is why auto manufacturers switched to using tempered glass. Tempering is a special process which makes the glass more shatter resistant.