The crescent-shaped Horse Heaven Hills region covers more than 600,000 acres, running about 60 miles long, from east to west, and about 22 miles wide, from north to south. Arching from the Wallula Gap to Kiona and to Wood Gulch near Roosevelt, the area has been mapped and remapped since 1904. Since then, various plans have been proposed to develop the land for irrigation purposes because a large share of the farm land in Benton and Klickitat counties lies in this region. About 1917, for instance, a plan called for diverting the Klickitat River to the area, but was dropped when the U.S. Indian Agency decided to use the water on the reservation. A later plan called for building a dam for the Columbia River at the Umatilla Rapids and use the power for pumping onto the Horse Heaven Hills area, but that proposal eventually died.

In 1969, the residents and landowners in the area organized a committee to consider Horse Heaven Hills agricultural development and entered a contract with the Agricultural Research Center of Washington State University to study the potential for such development and the impact that development would make. In 1970, the Horse Heaven Hills Study Group, composed mostly of representatives of the College of Agriculture at WSU, completed a study for the committee. The final report concluded that the bulk of the irrigable area would need a development involving some kind of canal system, and it also discussed the possibility of a storage reservoir at Paterson Ridge to be used as a cooling pond for a nuclear power plant to supply electricity to the region. The study group concluded that in general, irrigation development in the entire region would likely not be financially possible, but it did indicate the feasibility was great enough in a more limited portion of area to warrant further analysis.