When did nickels stop being made with silver?

During WWII special "war nickels" were made from an alloy of 56% copper, 35% silver, and 9% manganese. The composition was changed because nickel metal was needed for the war effort. War nickels were minted from late 1942 to 1945 and can be identified by a large mint mark letter over the dome of Monticello on the back.

All US other US nickels, regardless of date, are made of an alloy of 25% nickel and 75% copper.