The primary setting of BioShock Infinite is a city suspended in the air by giant blimps and balloons, called "Columbia", named in homage of the 'female personification' of the United States. Unlike the secret development of the underwater city of Rapture, Columbia was built and launched in 1900 by the American government to much fanfare and publicity.
On the surface, Columbia appeared to be designed as a floating 'Worlds Fair' that could travel across the globe; however, some time after its launch but before the game's events, the city was revealed to be a well-armed battleship, and became involved in an "international incident". The city was disavowed by the United States government, and the location of the city was soon lost to everyone else.
As a result of the city's isolation, a civil war eventually broke out on Columbia between different factions of citizens, each trying to seize control of the city from the powers-that-be. At the time of the game's events, only two main factions remain. One are the remnants of those retaining power over the city, whose spokesperson is an ultranationalist politician named Saltonstall. The city's ruling class, which seeks to keep Columbia purely for American citizens, denying foreigners the same privileges and a group named Vox Populi (Latin for "voice of the people"), a rag-tag resistance group opposed to the ultranationalists. The Vox Populi is formed from several factions with similar ideologies that fought to seize control and restore the rights of Columbia citizenship to all. However, years of war and struggle have driven the Vox Populi to fight the powers-that-be solely out of blind hatred, resulting in more violent and brutal methods and leading to subfactions in the group.