After WWII, Hanford continued to produce plutonium for the build-up of Cold War weapons; all told, Hanford produced more special nuclear material than any other place in the world. At its height in 1964, nine nuclear reactors or "piles" were operating on the banks of the Columbia, the powerful waterway flowing from Canada into the Pacific Ocean at the Oregon coast. These reactors were built during an era ungoverned by environmental regulations; eight of the nine piles directly contaminated the river, which is also the principal hatchery for Chinook salmon and steelhead trout. The waste contamination threatened the health and safety of people and wildlife in the area.

The majority of the radioactive and chemical waste was stored in 177 underground tanks built from the 1940s to the 1980s. Designed to last 20 years, the tanks held millions of gallons of waste; to date, according to the Department of Energy (DOE), 67 tanks have leaked an estimated 3.8 million liters of radioactive waste. When production was finally stopped with the fall of the Iron Curtain in 1989, Hanford faced a massive nuclear waste cleanup job.