Endangered salmon blocked for nearly a century from hundreds of miles of the Klamath River in Oregon and California are expected to return en masse under unusual agreements signed Wednesday to tear down four hydroelectric dams.

U.S. Interior Secretary Sally Jewell, who signed agreements with the governors of both states, said the plan would bring about one of the largest river restoration projects in the history of the U.S. The landmark deals also protect farmers and ranchers from rising power and water prices as the various interests work to end long-running water wars in the drought-stricken Klamath River basin.