In 1965, the United States government stopped making silver from dimes, quarters and reduced the amount of silver in half dollars. It wasn't until 1970 when silver was removed from dollar coins.
In 1933, silver became the standard in the U.S. due to the Great Depression and the rule that no Americans can own gold.
In 1964, the U.S. government started to make less silver coins due to a shortage in silver. The U.S. Treasury reacts by redeeming silver certificates for silver bullion, which drives up the value of silver in total.
In 1970, the Bank Holding Company Act requires that the dollar is made of a mix of copper and nickel called cupronickel.