U.S. Silver Coins were minted for circulation until 1964 at which point the spot price of silver got so close to the denomination of the coins that is was no longer economically feasible to issue these coins.  In addition, people had begun hoarding silver coins as silver prices increased and especially after 1965, when silver coins were no longer made but could still be found in change. 1965 is when the U.S. Mint started to introduce which is known as copper-nickel or cupro-nickel coinage. That is what you find in your change today.