Where were US quarters minted?

Quarters have been struck at 5 different mints since the denomination was first issued in 1796:

Philadelphia (no mint mark or "P"): 1796 to the present

Denver ("D") : 1906 to the present

San Francisco ("S") : 1855 to 1954

New Orleans ("O") : 1840 to 1860 and 1891 to 1909

Carson City ("CC") : 1870 to 1878