Alta Wind Energy Center (California state) : The largest onshore wind farm in the United States.

As of 2013, it is the largest wind farm in the United States, with a combined installed capacity of 1,547 MW (2,075,000 hp).

The project will "reduce carbon dioxide emissions by more than 5.2 million metric tons, which is equivalent to taking 446,000 cars off the road". A total of 3,000 MW (4,000,000 hp) is planned.

The wind farm was developed by Terra-Gen Power which closed a US$1.2 billion financing deal in July 2010 with partners that included Citibank, Barclays Capital, and Credit Suisse. Construction of the Alta Wind Energy Center is expected to create more than 3,000 domestic manufacturing, construction, and maintenance jobs, and contribute more than one billion dollars to the local economy.

According to wikipedia