When did the US stop making nickels out of nickel?

From mid-1942 to 1945 US nickels were made of an alloy of 35% silver, 56% copper, and 9% manganese because nickel metal was needed for the war effort.

All other US nickels minted from 1866 to mid-1942 and from 1946 to the present are made of an alloy of 75% copper and 25% nickel.