Hard to believe, but this year will be the  fortieth World of Concrete Expo. The first show was in February 1975, in Houston, Texas, with just three sponsoring organizations (American Society for Concrete Contractors, American Concrete Pumping Association and Concrete Construction Publications) and 2 participating organizations (American Concrete Institute and Portand Cement Association). Here's a look back at some of our favorite photos from those early days through now. See you in Las Vegas!