The 50 State Quarters program has expanded to include the District of Columbia and five United States Territories: Puerto Rico, Guam, American Samoa, the U.S. Virgin Islands, and the Northern Mariana Islands. The DC quarter is already in circulation and five territories' quarters will be issued periodically through 2009. Pictured is the Guam coin to be issued later this year. Read more here.
The 50 State Quarters program was extremely successful in renewing interest in coin collecting (also known as numismatics). So much so, that the U.S. Mint estimates that the program generated about $4.6 billion in seigniorage from coins taken out of circulation by collectors from the program's beginning in 1999 through about 2004.
Seigniorage is the difference between the face value of a coin and the cost of producing, distributing and retiring it from circulation. Since it costs the Mint around 5 cents for each 25-cent coin it produces, the government had revenue whenever someone chose to collect the coin and not to spend it.
In 2010, the U.S. Mint will begin a new program with quarters featuring national parks and other national sites. One site will be selected for each of the 50 states, DC, and the five territories. After all sites are selected, the quarters will be issued at the rate of five per year in the order in which each site was first established as a national site.
George Washington's profile will still appear on the obverse side of all the quarters.
[Thanks to Tracy for the idea for this post!]