How many different US quarters are there?

I collect United States quarters and I almost have a complete set but I keep finding ones like Guam, Puerto Rico, and District of Columbia. Other than the usual 50, (or 51 if you want to count the eagle) how many different quarters are there?

The original state quarters program had 50 different designs. Another program of 6 quarters was added for 2009 and they were Washington DC., Puerto Rico, Guam, American Samoa, U.S. Virgin islands and Northern marianas. The people living in these places are American citizens. It is a different program and is not part of the original state quarter programs for the territories above are not states. You can add them or not it is up to you. As for different types of quarters there are many from the silver Washington quarters all the way back to the Draped bust type of 1796. Most collectors agree the most beautiful is the Standing Liberty of 1916-1930. The territories quarters were distributed using no system, so they are out there but not easy to find. They will show up though.