The Works Progress Administration (WPA) was a government agency that sought to employ workers who were unemployed. Many were put to work on railroad lines, road crews, etc… They also employed artists to make posters promoting special events, publicizing attractions, etc…

Among the posters that they put together were a series on safety. Here are a few of the posters they put together:

Besides these safety posters, there are hundreds of old posters that you can reference. Check out the complete collection at http://www.loc.gov/pictures/search/?sp=1&co=wpapos&st=grid