Is there a 100 dollar coin in the US?

Answer 1

There's never been a circulating US $100 coin. In fact the $20 double eagle was the highest-value coin minted for circulation. However the Mint currently makes precious-metal bullion coins that have an artificial $100 denomination but they're not intended to be spent. They're sold to collectors and investors, and their actual value is determined by their metal content.

Historical note: In the 1870s George T. Morgan, designer of the Morgan dollar, proposed minting a $100 denomination that was to be called a "Union". However that was an enormous amount of money at the time and would also have been a huge coin - at least 160 grams - because gold was worth much less per ounce than it is today. The Smithsonian Institution recently contracted with a private company to mint silver reproductions of the design, but they sell for far more than their silver content is worth.