Slim Jim founder Adolph Levis began his career peddling condiments, relishes, cabinets, and pickled meats, but quickly found pepperoni to be his most popular product. Bar owners frequently bought his pepperoni, but the sticks were big, inconvenient, and messy to eat, so Levis set out to improve his snack.

In the early 1940s, Levis and his brother-in-law Joseph Cherry hired a meat packer to help innovate a new slim stick of dried, spiced meat that only took three months to cure. The new meat sticks were kept in small vats of vinegar behind the bar and quickly became a hit, and the brothers advertised their product as "less than a meal and more than a snack.”

Initially, the entrepreneurs named the meat stick "Penn Rose” after Levis' home state of Pennsylvania and his wife Rose, but it was later changed to Slim Jim and given a mascot to better promote the new product. They marketed the product on ashtrays not just as a more refined bar snack, but as a way to elevate one's drinking experience.

The pair gained enough success to launch their own food company, Cherry-Levis food products, and continued to sell Slim Jims in bars throughout the 1950s. Eventually, Levis decided to begin packaging the meat in individual cellophane wrappers, which allowed it to be sold in convenience stores and grocery shops rather than just bars.