United States Business Directory: USA is the ISO 3 alphabet country code of United States. Currency of United States is $, which has a short code of USD. Capital of United States is Washington, D.C.. United States has the population of 326766748 and approximate area is 9826675.00 square kilometers (or approx. 6106295.845 square miles). Population density of United States is approx. 33/Km2 (or approx. 20.5062/mile2)