The event, celebrated for over 49 years, has grown to one of the largest in the area and welcomes as many as 40,000 guests each year. We encourage you to tour the historic sites, enjoy the free concerts, explore our unique stores, and dine at our fine restaurants and cafes. Horse Trading Days is an annual event of the Zelienople-Harmony Business Association and is made possible through the support of local residents, businesses, police and fire police, Zelienople Borough, and many more. How did it all start? The first Horse Trading Days festival was introduced in 1963 by Ron Roach, Jim Cleaver, Franklin Health and Donald Waltman as a way of promoting the Harmony and Zelienople areas.