After graduating from Barstow High School in the mid-1940s, he moved to Los Angeles, working at MGM studios as a messenger boy. Following service in the Army Air Corps toward the end of Word War II, Mr. Petersen, now an independent publicist immersed in the burgeoning customized auto culture of California, was instrumental in creating the first hot-rod show at the Los Angeles Armory. To help establish the event, in January 1948 he launched Hot Rod Magazine, and hawked the magazine at local speedways for 25 cents a copy. Motor Trend, a more upscale publication for production car enthusiasts, and dozens of other titles aimed at specialty automotive segments soon followed.