Morgan Dollars minted in Denver, CO
The Denver mint first began striking coins in 1906 and is still in operation today. It was originally opened in 1863 to assay gold during the Pikes Peak gold rush. The Denver mint is the largest producer of coins in the world.
Mint marks are located appear underneath the tail feathers on the coin's reverse between the D and O of the word Dollar. Other additional city mint marks would include CC for Carson City, P for Philadelphia, O for New Orleans and S for San Francisco.