The Three Mile Island Nuclear Generating Station is located near Harrisburg, Pennsylvania. It consists of two pressurized water reactors, with Unit 1 operational since 1974 and Unit 2, which experienced a partial meltdown in 1979. This incident was the most serious accident in U.S. commercial nuclear power plant history, leading to significant changes in nuclear regulatory policies. Following the accident, the plant underwent extensive safety reviews and upgrades. Unit 2 was permanently shut down, while Unit 1 continued to operate until its closure in 2019. The site is now monitored and managed by the Nuclear Regulatory Commission and is undergoing decommissioning.