The area surrounding Pymatuning was shaped by glaciers more than 14,000 years ago. The land was dotted with dozens of kettle lakes as the ice melted away. Indians were attracted to the area due to its rich wetland habitat and number of wild animals. The first inhabitants around the lake were the Mound Builders. The lake was named for Pihmtomink, the leader of the Lenape tribe. Pymatuning translates as "crooked mouth man's dwelling place".

Pymatuning lake is a total of 17,088 acres and 17 miles long. It's average width is 1.6 miles with around 70 miles of shoreline. The maximum depth is 35 feet deep. The lake's capacity is 64,275,000,000 gallons of water. The state park has three beaches, seven picnic areas, five boat launches, three camping areas (tent and trailer, cabin camping, and primitive camping with 434 campsites and 10 primitive campsites, 5 privately owned campgrounds), and 2 hiking trails.

In 1911, a bill was passed allowing $10,000 to investigate the feasibility of a dam. Because of a major flood in 1913, the legislature approved $1.2 million for the construction of the dam, but Governor Tener reduced it to $100,000. Work began in 1931 with 7,000 men. The dam was completed in 1934. The dam cost a total of $3,717,739. In 1950, the Division of Parks and Recreations began developing Pymatuning State Park.

Pymatuning State Park is home to the bald eagle. Several pairs nest on the Pennsylvania side of the park. Along with the eagles, the park is home to numerous types of fish including walleye, crappie, black bass, bluegill and channel catfish