The Greenfields Irrigation District was established on January 1, 1931 to operate and maintain irrigaton canals in the Greenfields division of the Sun River Project in west central Montana.

The District diverts water from the Sun River below Gibson Reservoir to the Pishkun Reservoir and Willow Creek Reservoir via the Pishkun Supply Canal. Water released from Pishkun Reservoir enters the Sun River Slope Canal and is distributed to approximately 83,000 acres in the Greenfield Division.