Each Indian Reservation is subdivided in various ways. For example, the Navajo Nation is subdivided into agencies and Chapter houses, while the Blackfeet Nation is subdivided into Communities. The Federal government also maintains exclusive jurisdiction over military installations and American embassies and consulates located in foreign countries. Other special purpose divisions exist separately from those for general governance, examples of which include conservation districts and Congressional districts. According to the U.S. Internal Revenue Service,  The primary political entity of the United States is the state. Four states—Kentucky, Massachusetts, Pennsylvania, and Virginia—call themselves "commonwealths." The word "commonwealth" in this context refers to the common "wealth", or welfare, of the public. The term has no legal impact. In 1777 the 13 colonies that had declared independence from Great Britain one year earlier (July 1776) agreed to the formation of a confederation of states under the Articles of Confederation, with an extremely limited central government. A new national frame of government came into force in 1789, when the current U.S. Constitution replaced the Articles. This constitution incorporates the doctrine of the separation of powers, whereby the federal government is divided into three branches, as well as concepts of federalism, describing the rights and responsibilities of state governments and of the states in relationship to the federal government. On numerous occasions the United States Supreme Court has affirmed that the 50 individual states and the United States as a whole are each sovereign jurisdictions under the Constitution. Due to the shared sovereignty between each state and the federal government, Americans are citizens of both the federal republic and of the state in which they reside. States, however, are not sovereign in the Westphalian sense in international law which says that each State has sovereignty over its territory and domestic affairs, to the exclusion of all external powers, on the principle of non-interference in another State's domestic affairs, and that each State (no matter how large or small) is equal in international law. Additionally, the 50 U.S. states do not possess international legal sovereignty, meaning that they are not recognized by other sovereign States such as, for example, France, Germany or the United Kingdom. The 50 states of the United States of America are as follows (this list includes both the postal code abbreviation and the traditional abbreviation for each state):    The 50 states can be divided into regions in many different ways. The states are divided into smaller administrative regions, called counties in all but two states. In Alaska, the county equivalents are called boroughs (parts of the state which are not included in any borough are considered part of the Unorganized Borough, which itself is divided into census areas), and in Louisiana, the county equivalents are called parishes.