Builders have broken ground at Alta Wind Energy Center in the Mojave desert in central California, which is earmarked to host 1.55GW.
Once complete, the Terra-Gen Power project will dwarf E.on's 782MW facility at Roscoe, Texas, and NextEra's 736MW Horse Hollow complex, also in Texas.
The project has been backed by California's pro-renewables governor, Arnold Schwarzenegger.
"Having the world's largest wind project break ground in our state is tangible evidence that our pioneering policies are drawing investment," says the former Hollywood star.
Big break for largest wind farm in West
US - Construction has begun on what is planned to be the largest wind farm in the western world.
