United States of America Government Constitutional republic; UN Member State (1945) Capital Washington D.C. Population 331 893 745 Land area 9 800 000 km² Max height above sea level 6 191 m EEZ 11 700 000 km² Currency US dollar (USD) Languages English GDP per capita 692 875 USD Useful links U.S. Department of State U.S. Embassy in Fiji, Kiribati, Nauru, Tonga and Tuvalu USAID Pacific Community Membership 1947