(WHTM) — Only one state generates more nuclear energy than Pennsylvania.

The Commonwealth has four active nuclear power plants, according to the PA Emergency Management Agency.

The power plants are:

• Beaver Valley Power Station in Beaver County
• Peach Bottom Atomic Power Station in York County
• Susquehanna Steam Electric Station in Luzerne County
• Limerick Generating Station in Montgomery County

Pennsylvania’s output accounts for one-tenth of the nation’s nuclear energy generation in 2023, and about 32% of the state’s electricity net generation, according to the United States Energy Information Administration. Only Illinois generates more nuclear energy, thanks to its six plants.

Nuclear energy has a long history in the state. The nation’s first commercial nuclear reactor, and the world’s first devoted to peace-time activities, opened in 1957 in Shippingport, Beaver County. The reactor operated for 30 years.

Perhaps the most-known nuclear reactor in Pennsylvania is Three Mile Island’s Unit Two reactor, which partially melted down in 1979. It was the most serious nuclear power plant accident in U.S. history.

While Unit Two shutdown after the accident, the plant’s Unit One reactor operated until 2019.

This didn’t mark the end of nuclear power in the state, though. Last year, Constellation Energy announced plans to restart Unit One at Three Mile Island to provide power for Microsoft data centers.

In June, Amazon announced it plans to build a data center next to the Susquehanna plant near Berwick, where it intends to get its power.

The center would require 960 megawatts of electricity, or 40% of the plant’s output.