When was the last year when US cents were produced with solid copper?

The last year that the US minted a solid copper cent coin was in 1857. These were called Large Cents because they were about the size of half-dollars.

After that were Flying Eagle and Indian Head cents that were .880 copper and .120 nickel. In 1864 the composition was changed to .950 copper and .050 tin and zinc. Then came the Wheat pennies, and they were .950 copper and .050 tin and zinc (with the exception of 1943, which were Zinc coated steel).

1959 to 1962 Lincoln Memorial came next with .950 copper and .050 tin and zinc. 1962-1982 were .950 copper and .050 zinc.

Lastly 1982 to date are .975 zinc and .025 copper.