The mint mark on a Morgan silver dollar can be found on the eagle (back) side of the coin, just above the word "DOLLAR" written around the bottom edge. The coin may also have small letters located above the "D" and the "O," indicating the location of the mint.
The following is a key for determining the mint location of a coin: Carson City (CC), Denver (D), New Orleans (O) and San Francisco (S). If no letter is found, Philadelphia is the minting location. Any combination of these mints produced the Morgan silver dollar from 1878 to 1904. The mints did not produce any of these coins from 1905 to 1920 due to the rise in popularity of the paper bill. The Morgan silver dollar made a brief return in 1921 before the Peace silver dollar became the favored form of silver currency.