Some US coins retained a silver content into the 1970s, but that was just tradition. The US was not on the silver standard. Instead, the US had been on a gold standard until 1933, when Rooselvelt demonetized gold and made the possession of gold for monetary purposes illegal. Owners of monetized gold were forced to convert it at the nominal value within 14 days. Afterwards Roosevelt fixed the gold price at 35 dollars per ounce, resulting in a devaluation of the dollar to 59% of its last gold value. Gold holders were effectively expropriated at a grand scale. The next strike against gold came in 1971 under Nixon. The US government had promised foreign governments that had pegged their currency to the US dollar a fixed conversion rate to gold. Because of the Vietnam War and large scale social programs, the US government over issued dollars in the 1960s. When the French and Germans demanded the US government to honor their promise, Nixon declined, basically saying "You keep the paper, we keep the gold". The over issuance of dollars in the 1960s and the resultant downward pressure on the USD had forced the pegging countries to expand their money supply to maintain the peg, causing them to import US inflation, which resulted in the stagflations of the 1970s and the suffering of millions of people. So, while nobody really cared about the silver content of the dollar coins, the abolition of the gold standard in 1933 and 1971 has caused many people to lose their savings, jobs and livelihoods.