At the start of World War II, a general store owner in Missouri was having a very hard time filling the orders of some of his customers. They were in need of dustpans. Because of the metals rationing, manufacturers simply weren't making them at the time.
It was then that he remembered that he had some old license plates. Why not use them instead of letting them just sit and rust? Thus, the very first of the license plate dustpans came to be. It is only more recently that people have begun recycling this not-so-new idea.