Before the events of The Hunger Games, District 13 was part of the nation of Panem. Its main industry was military arms manufacturing and the production of nuclear weapons, and it also specialized in graphite mining as a secondary industry.
Before it seceded, District 13 was known for mining graphite, but its hidden industry was nuclear technology. District 13's underground facility later became the center of the new rebellion.
District 12, however, is still the smallest and poorest district in all of Panem. District 12's primary industry is coal mining, an industry that took the life of Katniss' father when she was just 11-years-old.
How long before Hunger Games was District 13 destroyed?
Located in far northeastern part of the country, District 13 was widely thought to have been destroyed by the Capitol during the climax of the First Rebellion (74 years prior to the events of The Hunger Games trilogy).
Everyone's in the districts was made to believe district 13 was destroyed to serve as a warning but they really signed a peace treaty with the Capitol to avoid either using nuclear weapons at each other.
In Mockingjay P1, when Coin gathers D13 to announce the tributes full pardon, Katniss observes that there's hardly any children in the district. Prim explains there was an epidemic that killed most of them.
Since District 13 specialized in nuclear weaponry, the Capitol quickly surrendered and agreed to a peace deal. They both agreed that the residents of District 13 would all move underground and the land above would be bombed to make it seem like the Capitol had won.
In order to survive, the people of District 13 had developed innovative technologies that allowed them to maximise available resources, as well as a strict, militaristic lifestyle that emphasized frugality and a constant readiness to defend themselves against potential attacks.
District 12: District 12 was the smallest and poorest district in Panem. The district was located in Appalachia and their main industry was coal mining.
Now, the District 12 refugees have been welcomed into District 13, whose population is waning because of a pox epidemic that killed many of the district's citizens and left a great number of them infertile.
Without adequate weaponry to fight back, the Capitol was forced to allow District 13 to secede. While District 13 had the option of defeating the Capitol with nuclear weapons, they chose not to, as their actions could have wiped out nearly all of the population.
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.
To the knowledge of Panem's citizens, District 13 was completely destroyed by the Capitol during the First Rebellion, and it remained inhabitable during the events of the main series. At least, that's what they were led to believe. As revealed in Catching Fire, District 13 was very much up and running.
The following year after Lucy Gray Baird's victory, another female tribute emerged as the Hunger Games winner. Mags Flanagan became the first victor from District 4, living off of nuts and her survival skills by creating fishhooks. She was also the first victor to move to Victor's Village before serving as a mentor.
District 13 is more egalitarian but different than communism. While I agree in theory that in in Communism everyone would be poor, there would still be class differences in practice, though not socially accepted / acknowledged. It would be about all 'having' the same (not necessarily 'being' the same).
District 12 has the most Hunger Games victors, with five winners, including Katniss, Peeta, Haymitch, and Lucy Gray. Finnick Odair is the youngest winner in history, winning at just 14 years old.
After Katniss and Peeta won the 74th Hunger Games, they joined Haymitch in District 12's Victors' Village. Considering everything known about the 12 districts that participated in the Hunger Games, it's a fair assumption that the district with the least number of victors was District 12.
Destruction. At the end of Catching Fire, Gale sees Katniss on her way to District 13 and informs her that there is no District 12. The district was destroyed with incendiary bombs by the Capitol, with only the Victors' Village spared.
District 11 also seems to be one of the poorer districts; the citizens are not allowed to eat any of the crops- presumably because nearly everything is reserved for the Capitol- and Katniss Everdeen describes the local housing as poor, even compared to the Seam in District 12.
Katniss and her family come from District 12, a coal-mining district that is the poorest, least populated, and smallest district in the dystopian fictional autocratic nation of Panem, ruled by the Capitol.
Given that she is willing to make the ultimate sacrifice to protect Peeta, it's safe to assume that the Morphling was committed to the rebel cause. Like the other victors, she knows the power that Katniss has as a lightning rod for the rebellion, and she knows that Katniss will not help without Peeta.
Peeta's warning District 13 of the imminent bombings places him in great danger, yet he still does everything he can to protect Katniss and keep her safe. By warning District 13, the district's citizens have enough time to make it into the deep bunkers.
Ultimately, Dr. Gaul considered these games a disaster, presenting the Capitol as far too vulnerable. She erased all recordings of the games, keeping only a master copy in her own personal vault for her own purposes.
