In 1903, Milton S. Hershey, founder of the Hershey Chocolate Company, surveyed the town that would become Hershey. Included in his plans was a site along Spring Creek that would be suitable for a leisure park for Hershey employees. In 1905, a bridge was built over Spring Creek, and a pavilion was built on the hill that overlooked it. While the bridge was able to be constructed, the land on the banks of Spring Creek, from Derry Church to Union Deposit, and areas further north of the creek (including the area currently occupied by Hersheypark Arena and Stadium) was then owned by J.H. Nissley. In February 1906, Hershey purchased all but two tracts of land, near Union Deposit, from Nissley. In early spring, the Hershey baseball club staked out an area for a baseball field; a baseball diamond, a track surrounding the field, and grandstands were built. The first game was played on May 5, which was a 4–0 loss to Felton Athletic Club. This is also noted as the first open-air event in Hershey.

On Wednesday, May 30, 1906, Hershey's park was opened to the public and formally called Hershey Park. The festivities included a baseball game, in which Hershey defeated the Crescent Club of Harrisburg by a score of 13–1. Music was performed by the recently formed Hershey Band and other events were held on park grounds. Prior to that time, the park had been called various unofficial names, including "West-end" Park and Hershey's Park, which (despite being a popular, and grammatically correct, choice) was picked over in order to combine the words Hershey and Park. In 1970, after more than 60 years of operation, park management decided to redevelop the park into a theme park. The name was changed to Hersheypark in 1971, and it has operated under that name ever since.

The first ride was added to the park in 1908 – an Allen Herschel carousel often referred to as the "Merry-Go-Round". This was followed in 1910 with the addition of the Miniature Railroad, which remained in operation until the end of the 1971 season. The park has operated a bumper car ride since 1926, a variety of boat rides on Spring Creek, and six dark rides, three of which were fun houses. The park added its first two kiddie rides in 1926, The Prowler and The Regurgitator, and has added well over 40 since then.

The park added its first roller coaster in 1923, the Wild Cat, for the town of Hershey's twentieth anniversary, which operated until 1945. It was replaced by the park's second wooden roller coaster, Comet, in 1946. Between then and 1996, the park added six roller coasters, including SooperdooperLooper, the first complete-circuit, modern-day looping steel roller coaster on the East Coast of the United States, which opened in 1977. In 1996, Hersheypark added its third wooden roller coaster (Wild Cat and Comet being the first two), naming it Wildcat (initially The Wildcat) after the original Wild Cat. Between the 1996 addition of Wildcat and 2015, the park added nine roller coasters. This included the hypercoaster Skyrush in 2012, the multilooper Fahrenheit in 2008, the launch coaster Storm Runner in 2004, and the inverted coaster Great Bear in 1998.

Of the coasters that the park has had, only five are no longer in the park: a twin roller coaster called Toboggan (also called Twin Towers Toboggan or Twin Toboggans) which was located in Carousel Circle; a water coaster called Roller Soaker which was in Midway America and later The Boardwalk; a kiddie coaster with an oval track called Mini-Comet; the 1996 Wildcat; and the original Wild Cat. The station of the Wild Cat was located in the Minetown area where the Convoy ride is currently, with most of the out-and-back layout/structure built along the north side of Spring Creek between the base of Storm Runner's first drop and the station for Trail Blazer. "Candymonium" is the tallest, fastest, and longest roller coaster at Hersheypark.

The park has had several pools, the first located next to Spring Creek in Comet Hollow, the area themed as The Hollow as of 2018. The first pool operated from 1908 until 1911, which included a toboggan-slide ride called Shoot-the-Chutes. This pool was replaced by a cement pool which opened in 1912 and remained in use through the 1928 season.

That pool was replaced by a new pool complex on the western edge of the park, which included a large bathhouse, one large pool and a smaller pool, as well as a beach-like area and a lighthouse. It operated until 1971, when it was closed at the start of the Hersheypark theme park conversion renovation.

Hersheypark did not add another pool until 2007 when The Boardwalk at Hersheypark opened. It is a small wave pool for children, called Bayside Pier. That was followed by the addition of a much larger wave pool, called The Shore, which opened in 2009.

Hersheypark developed a number of themed areas, the first being Carousel Circle, Der Deitsch Platz, and Animal Garden in 1972, followed by Tower Plaza in 1975, Pioneer Frontier in 1985, Midway America in 1996, as well as The Boardwalk at Hersheypark in 2007. In 2014, Hersheypark merged several theme areas – Tudor Square, Rhineland, Founder's Circle and Music Box Way, became an area called Founder's Way, while the coal mining region themed area Minetown was re-themed as Kissing Tower Hill. The themed areas had featured different music to each area, such as polka-style songs being played in Der Deitsch Platz and Carousel Circle, country music being played in the Pioneer Frontier themed area, the Beach Boys being played near Tidal Force and later in The Boardwalk, as well as Ragtime and jazz music being played in Midway America. However, the music was phased into being the same across the park, except in The Boardwalk and Pioneer Frontier. In the summer of 2020, Hersheypark opened a new themed area called Hershey's Chocolatetown, which included a new entrance plaza, ice cream parlor, flagship retail store, and a Bolliger & Mabillard hyper coaster named Candymonium. This includes the first ever Starbucks inside the park.