The Columbia River Interstate Compact is a partnership of the states of Washington and Oregon through which the fish and wildlife departments of the two states set commercial fishing seasons on the lower Columbia River. For this purpose the river is divided into five fishing zones between the mouth of the river and Bonneville Dam, a distance of 145 miles. A separate fishing zone, Zone 6, is designated between Bonneville and McNary dams, a distance of 147 miles, exclusively for Indian fisheries.
In establishing fisheries in zones 1-5, the Compact must leave enough fish for harvest in Zone 6 to meet the legal requirement that Indian fishers are entitled to half the harvestable surplus of fish in the river. Indian fishing is regulated under the ongoing U.S. District Court litigation known as U.S. v. Oregon.
The Columbia River Compact dates to 1915, when it was established by Washington and Oregon to resolve the chaos that resulted every year when the states established and tried to enforce their own commercial fishing seasons and regulations. The compact provides that neither state may change its fishing regulations, which are identical, without the consent of the other. Congress approved the Compact in 1918.