This was one of the two American plutonium production sites, together with the Hanford site. www.youtube.com/watch?v=qwKhz7BPBLY mentions it produced about 1/3 of the total American plutonium.
www.reuters.com/article/world/americas-nuclear-headache-old-plutonium-with-nowhere-to-go-idUSKBN1HR1JT/ claims that as of 2018 it stored the majority of the plutonium stockpile of the country.