The Hershey Abattoir was a meat and commissary company which produced products for Hershey Estates (which was later renamed HERCO, Inc., and is called Hershey Entertainment & Resorts Company today). One such product was the Hershey Estates Hot Dog was originally sold in Hersheypark. These hot dogs were apparently good enough that the Abattoir started selling them in packs and advertising them in local newspapers in the 1950s.
On April 17, 1975, the Abattoir began advertising that the Hershey Estates Hot Dogs had been rebranded to Hersheypark Franks. Here is an advertisement for the product, in the Lebanon Daily News on page 17.
In 1980, Hershey Abattoir became Hershey Meats and Commissary. In 1993, the Commissary was sold to Hatfield Quality Meats. Hersheypark Franks were discontinued shortly after that when Hatfield was required to discontinue using the Hersheypark trademark.