Panem

Panem is the country where The Games takes place, and is the home to all of the events of the Hunger Games universe. So far, it is the only country currently known to exist.

History
The history of Panem is that of a future North American continent. Precisely how far into the future is unknown, though it is several hundred years at the very least.

Prehistory
Panem used to be what we know as the United States, Canada, and the northern and central portions of Latin America. However, sometime in the past, an unknown cataclysm occurred which caused sea levels to rise rapidly and unexpectedly. The resulting floods, fires, and related disasters caused entire nations to disappear and nearly wiped out human civilization. It also changed the shape of the continents, and in the case of North America, entire cites and even states and provinces were completely submerged.

Another side effect of the cataclysm was the loss of almost all knowledge from before the sea levels rose; very little information about the world before this has been preserved, and few people know anything about the history, culture or technology of the pre-cataclysmic Earth, save for those things that were carried over into Panem. So far, the only known remnants of the previous civilization known to exist are the few works of art that are displayed in the Capitol, and the teleportation technology beneath District 2, though the latter is technically classified information.

Formation of Panem
Exactly when Panem formed is also unknown, as is its original form and layout. Some theories suggest that the Districts were once independent nations that arose from the cataclysm and that the Capitol found the means to conquer or unite them all. In any case, the country of Panem was formed at least a century ago, and the Capitol became the seat of Panem's government, controlling and facilitating the flow of goods from the Districts.

The Rebellion
Eventually, the Districts rebelled the increasingly corrupt Capitol. Led by District 13, all of the Districts banded together and fought against the Capitol forces. Exactly when the rebellion began, and how long the rebellion lasted, is unknown. It is known, however, that the rebellion was crushed 75 years ago with the bombing and obliteration of District 13. Afterwards, all of the remaining Districts surrendered.

In response to the rebellion, the Capitol forced all of the Districts to sign the Treaty of Treason, an accord which afforded the Capitol almost unlimited power and transformed the Districts into virtual slave colonies. Nearly all of the resources the Districts produced were sent to the Capitol for consumption, leaving many Districts to live in states of poverty and near-starvation. The Treaty of Treason also created the Hunger Games and required the Districts to send two children between the ages of 12 and 18 - one boy and one girl - to participate in them every year.

74th Hunger Games
The Hunger Games continued for 74 years almost unchanged and uninterrupted. However, the 74th installment of the Hunger Games changed everything. Katniss Everdeen and Peeta Mellark, the District 12 Tributes, made a suicide pact to kill one another as the final two contestants in front of the entire nation. If carried out the pact would cause the Hunger Games to not have a winner for the very first time. Quickly the rules were changed and both Tributes were announced as the winners, but the damage had been done; several Districts saw the act as one of rebellion and began to rise up once more.

In response, President Snow ordered his men to use Panem's technology to augment the teleportation technology found in District 2, which would allow for Tributes to be brought from other worlds and times for the next year's Quarter Quell. (Edit: the Tributes that participated in the Quarter Quell were selected from the pool of surviving victors from previous Games, not “teleported in from other times”.)

Government
The government of Panem is, for all intents and purposes, an oppressive police state, where the populace is kept in line both by the use of fear (the Peacekeepers and the liberal use of capital punishment and torture for most citizens in the Districts) and entertainment (The Hunger Games). The use of controlling goods also keeps the Districts unable to rebel; as most food and supplies go to the Capitol, those in the Districts are left with little nourishment or supplies to put up a sustained fight and must rely on the government for what little they can get. On the other hand, those Districts favored by the Capitol (and those who obstensibly have winning Tributes in the Hunger Games) are rewarded for their loyalty with more food and better living conditions, which widens the poverty gap between many Districts even more.

The current leader of Panem is Coriolanus Snow, who has served as the President for at least 25 years.