As of now, the largest power plant in the U.S. by capacity is the Grand Coulee Dam, which is located on the Columbia River in Washington State. It has a generating capacity of about 6,809 megawatts (MW). However, it's important to note that the Grand Coulee Dam is a hydroelectric power plant. If you are looking for the largest power plant in terms of other types of energy (such as fossil fuels or nuclear), that distinction might go to a different facility. For instance, the Palo Verde Nuclear Generating Station in Arizona is the largest nuclear power plant in the U.S. by net electrical power rating, with a capacity of around 4,000 MW.