Featuring 58 Vestas V100 1.8MW turbines, the Palouse project started commercial operations in December 2012 and is located near Oakesdale town.
The output from the project connects to the Avista 230kV Benewah-to-Shawnee transmission line.
Power generated from the project, which will provide enough energy for about 30,000 homes in Eastern Washington, will be sold to energy firm Avista.
Currently under construction near Amarillo, the Route 66 wind farm features 75 Vestas V110 2MW turbines and will power about 49,000 homes per year while delivering energy to the Electric Reliability Council of Texas market.
The wind farm is scheduled to be completed in 2015.
First Wind said it will continue to operate and manage both the projects.
First Wind CEO Paul Gaynor said: "Attracting strong investors such as those advised by J.P. Morgan Asset Management reinforces that First Wind is building high-value, financially viable projects.
"This transaction also provides First Wind capital to continue our efforts to develop and build new clean energy projects.
"First Wind will continue to operate the projects, as we grow our operations capabilities. We will continue to focus on serving our local communities in Washington and Texas while generating cost-competitive clean energy to homes and businesses."
