The Bland–Allison Act, passed by Congress on February 28, 1878, required the Treasury to purchase a minimum of $2 million in domestically mined silver per month and coin it into silver dollars. The Mint used a new design by engraver George T. Morgan, and struck what became known as the Morgan dollar. Many of the pieces quickly vanished into bank vaults for use as backing for paper currency redeemable in silver coin, known as silver certificates. In 1890, the purchases required under the Bland–Allison Act were greatly increased under the terms of the Sherman Silver Purchase Act. Although the Sherman Act was repealed in 1893, it was not until 1904 that the government struck the last of the purchased silver into dollars. Once it did, production of the coin ceased.
During World War I, the German government hoped to destabilize British rule over India by spreading rumors that the British were unable to redeem for silver all of the paper currency they had printed. These rumors, and hoarding of silver, caused the price of silver to rise and risked damaging the British war effort. The British turned to their war ally, the United States, asking to purchase silver to increase the supply and lower the price. In response, Congress passed the Pittman Act of April 23, 1918. This statute gave the United States authority to sell metal to the British government from up to 350,000,000 silver dollars at $1 per ounce of silver plus the value of the copper in the coins, and handling and transportation fees. Only 270,232,722 coins were melted for sale to the British, but this represented 47% of all Morgan silver dollars struck to that point. The Treasury was required by the terms of the Act to strike new silver dollars to replace the coins that were melted, and to strike them from silver purchased from American mining companies.
Article Source: en.wikipedia.org