The 121-turbine site is spread across 121 square kilometres in Clay and Dickinson Counties in northwest Iowa and will use GE’s 2.5-116 models.
When Apex Clean Energy announced the project in December 2015, the company envisaged a completion date of 2018.
Now Apex has developed the site, the Alliant subsidiary, Interstate Power and Light Company, will build and operate it.
Power from the project will be delivered into the regional electrical grid, Apex said.
In 2016, Alliant Energy vowed to spend $1 billion in adding up-to-500MW of wind capacity in Iowa by 2021.
Doug Kopp, president of Alliant Energy’s Iowa branch said: "This project will add millions of dollars in additional property taxes to the local communities and lease payments to landowners."
Late last month, Apex also announced the sale of the Dakota Range I and II sites — which have a total planned capacity of 300MW — to utility Xcel Energy.
Apex anticipates develop of 1.5GW of wind capacity this year and to annually increase this figure by 2GW to 2020, it said.