This historical encyclopedia examines the development of governmental structures from ancient times to the present. From Sumerian Ur to the Roman Empire, the ancient world provides prototypes of city states, hereditary kingdoms, tribal confederations, democracies, oligarchies, republics and empires. Powerful new empires and barbarian kingdoms appear in the early middle ages. The cities of renaissance Italy experimented with republics, communes and hereditary rule during the pre-modern era. The age of exploration led to great colonial empires. A wave of revolution produced the beginnings of nation states. The twentieth century witnessed the formation of new autocracies, the end of colonialism and the breakup of the communist bloc. Each of the 272 entries focuses on one of the 192 members of the United Nation or a historic governmental entity. Articles are arranged chronologically by period, which allows comparisons of contemporary governmental forms. Coverage is world–wide with every continent represented by indigenous cultures and modern nations. Entries on most contemporary nations are arranged according to their date of independence, formation, or current constitution. Each entry outlines the country’s type of government, historical background, important governmental structures, political parties or divisions and significant events shaping governmental affairs. In general, discussions tend to emphasize contemporary governmental structures, making historical coverage necessarily selective. Thus, the discussion of the Netherlands outlines the modern constitutional monarchy and not the Dutch Republic. Other nations, like China, earn multiple entries for different time periods. This introductory survey is suitable to high school, public and undergraduate library collections.