Hawaii got the last quarter at the end of 2008.So the US Congress passed a law and quarters in 2009 were for DC and the 5 US territories.Starting in 2010, quarters will be issued honoring national parks.
from 1999-2008, the united states treasury has been making quarters with different states on them each year, five a year, now they are making them with washington dc, guam, puerto rico and the other territories of the united staes, next year i think they will be doing national parks, then monuments
Because the U.S. treasury decided to include the territories in the series of quarters with all the states on them.