Answer:
It depends on the coin. Things such as the Presidential Gold Dollar coins and Sacajawea dollar coins are made out of brass and not gold. However, historically the US has made coins out of gold however, all those gold coins were minted before the mid-1930s. There are also the Gold American Eagle coins which state the amount of ounces of gold on the reverse of the coin and they are still being minted and those are made out of real gold.