They did not make Morgan silver dollars in 1979. If it is an 1879 the mintmark is located on the revers or back of the coin below the wreath. Hope this helps.
How Do I Tell What Mint My 1979 Morgan Silver Doller Is?
There are mintmarks underneath the tail feathers of bald eagle. They are on reverse between letters D and O. Mintmarks abbreviations mean:
Blank for Philadelphia mint
CC for Carson city mint
D for Denver mint of Denver,Colorado
O for New Orleans mint
S for San Francisco mint
Blank for Philadelphia mint
CC for Carson city mint
D for Denver mint of Denver,Colorado
O for New Orleans mint
S for San Francisco mint
Here is a page with the picture of the markings on a morgan silver dollar. Hope this helps. Www.swissamerica.com/article.php?art=04-2004/200404130244f.txt