As the supply of newly discovered gold in California came onto the world markets in 1848, the price of silver vs. gold rose, resulting in a dearth of U.S. silver coins in circulation. The answer was a gold dollar, and Congressional legislation approving this coin (as well as the Double Eagle) became law on March 3, 1849. For the next forty years, the diminutive gold dollar was struck at five different mints in three distinct types. As a Date set, the undisputed key is the 1875, with a miniscule mintage of only 400 pieces struck only at Philadelphia. Some of the other scarcer dates are the late Civil War issues (1863-65) and early reconstruction era coins (1866-72). Avoiding some of the scarce "C" and "D" mints though, permit this set to be completed for a reasonable outlay and within a fairly short period of time.