Although dollar coins have been minted intermittently since 1794, currently there are two dollar coin series in production: The Presidential $1 Coin Series (begun in 2007) and the Native American $1 Coin (first issued in 2009).
The two dollar coins are golden in color, created by a mixture of metals (none of them gold). These dollar coins have the same "electromagnetic signature" as their predecessor, the Susan B. Anthony (SBA) dollar, which was silver in color. Keeping this signature allows older vending machines to accept the new coins without being retrofitted.
When you hear the word "dollar," you may think first of the basic unit of money in the United States, whether paper or golden coins. But our first dollars were coins made of silver. The word "dollar" comes from the German word "Thaler," which was a large silver German coin.
Because these silver "Thalers" were popular everywhere, other countries began making their own versions. American colonists were used to the "Spanish dollar," a coin often used in the nearby lands that traded with the colonies. So "dollar" was a pretty easy choice as a name for the brand-new currency of the United States.
The dollar was one of the first silver coins made, back in 1794. Since then the dollar coin has been minted periodically with different versions of Liberty and other individuals on the obverse, including those of President Dwight D. Eisenhower (made 1971–1978) and suffragist Susan B. Anthony (1979–1981, 1999).