Idk if y'all are on TikTok and have seen Lucky Leftie's videos on each of the Districts, but she is amazing and really dives into the worldbuilding of each District and the importance of their industry in Panem. HOWEVER, she never got to D13. And since I've gotten a decent amount of asks regarding my thoughts (which OMG thank you all so much I literally love you all sm) i thought I'd make one.
Thirteen is probably the second most explored District in canon, so luckily I have a lot to go off of. BUT, a lot of this is comprised of headcanons that I attempted to connect to actual canon in the most realistic way possible. That being said, I reference my fic Just As it Was (ch 10 and onward) a decent bit because I had to world build 13 to write the setting for the later half of that fic.
Let's start with history and geography. D13 is located in what was once the Northeastern US and parts of Southeastern Canada. It includes parts of New England, Pennsylvania and New York, as well as Quebec. What I find really interesting is that there is an "underground city" aka RESO located in Montreal, Canada. It's essentially a shopping center, but also connects lots of hotels, and residences. Its HUGE. I think Suzanne Collins MIGHT have based the whole "underground city" on RESO. Katniss says the bunker in D13 was the work of centuries, and very valuable to the Capitol. It is also mentioned that they mine graphite (which is a used in nuclear reactors as a moderator or reflector). The Snow family, as mentioned by Coriolanus, held stock in the research labs and munitions factories in D13.
This gives us three industries to explore. I think, similar to District Two, there was a class distinction between the miners and those who worked in labs or produced munitions. Because D13 was the Capitol's main military stronghold, I can assume they were treated somewhat better than other districts due to their military advantage. This may have led to a relatively close relationship with the Capitol, similar to D2 at the time of the 74th games.
D13 is very close to two technologically advanced districts, D3 (technology) and D6 (transportation). I think before the first rebellion, they were able to collaborate and work together, which was terrifying for the Capitol. I think the development of the districts in terms of industry in Panem kind of mirrors the development of the United States. The more technologically advanced Districts are located on the east coast, where the west and central Districts are more focused on raw resource production. With the exception, of course, being the Capitol.
I think this is an interesting choice, but quite a smart play on the Capitol's part. On one hand, they have their most militarily equipped citizens far away enough to make a ground assault relatively impossible, and, incase they were attacked from the West and the Capitol was decimated, their weapons are stored far away, and those who survived had a bunker to confine themselves to wait out the enemy.
Which leads us to the first rebellion, in which 13 led and was then destroyed because of it. I think there was a lot at play here. I think D13 did not initially begin the rebellion, but they seceded to the rebels in neighboring, less fortunate districts and lent their weapons. But the Capitol recognized them as the leader because they are what made the rebels a legitimate threat. And that threat needed to be eliminated in order to quell any hope of a rebellion happening in the future.
So the Capitol bombed 13. However, I don't think that many of the citizens in 13 expected this because of their close relationship with the Capitol in the past. Which leads me to the first OC of mine, Arvada Coin (Alma Coin's grandfather). I think that 13 was headed by a General, rather than a mayor, because they're military. I think this general would not have accepted that their District was going to be destroyed. But some of his officers knew that the threat was not an empty one. Arvada Coin, who had lived underground his entire life because that was the industry his family worked in, pleaded for the General to issue a shelter in place warning and force everyone underground. When he refused, he defected from the military and began trying to get everyone to safety. In the end, he was able to save around half of the district, and the others all died in the bombings.
I think that's why the Coin family is so respected in D13. I think it was some initial forethought that ended up saving the lives of thousands.
Anyway, Coin is military, everyone under his direct command is military. They're all excellent at fighting, but none of them know anything about how to feed, clothe, and provide medical care for thousands of people. They have an excess of luxuries like electricity (nuclear reactors are INSANLEY good at what they do) and weapons but their citizens are starving because they've been cut off from all the rations from D4, D9, D10, and D11. Four whole districts are dedicated to food production and 13 has to find a way to cultivate crops with no arable land above ground and no sunlight. So they start with grain. They strip their hangars that used to house military equipment and devote them to agriculture. As I said before, they have an excess of electricity, so they are able to constantly power UV lights. So their food grows twice as fast, and there's no cold season underground. So they don't starve, despite the Capitol thinking they will.
But you can't eat only grain. So they turn to their allies. Just as the Plinths moved to the Capitol after siding with them during the war. I think some high ranking rebel officers and their families were allowed into D13 in order to escape the fallout from the failed rebellion. Two important people are Lt. Commander Finnegan, a D4 naval officer who served under Commander Harrington (Pup's dad) but defected and joined the rebels and Cera Hadley (Mrs. Hadley), wife of an important munitions dealer in D2 (who was Strabo's childhood best friend, but that's a long story). Commander Finnegan, being from D4, was able to create a fish farm in D13 (look up underground fish farms, THEY'RE SO COOL AND INSALEY EFFECENT). Cera Hadley knew the basics of gardening (thanks, Vesta (Ma) Plinth, for teaching her that btw. We're deep into the OC content now) and was able to cultivate plants important for resolving nutrient deficiencies, most notably, wood sorrel for treating vitamin C deficiencies. Limes, lemons, and oranges are notoriously hard to grow in cold climates, and orchards take up too much space. So they grew sorrel, and were able to modify their crops to grow underground and twice as fast.
And they survived, and grew more advanced with every year that passed, until they were able to become the powerhouse we saw in THG trilogy. But they stayed bitter, especially Coin, because of what they had to go through at the hands of the Capitol. So not only did they have a desire to protect the Districts, but also a desire for revenge which I think provided a lot of motivation for Alma (President) Coin.
I could talk about this forever, but I'll leave it at that! Thanks to @mr-nauseam, @maidstew, and @tumblingghosts for asking about this! I'm sorry if I gave you more than you asked for, but I simply have so much to say.
If your interested about D13 and learning about it in less "info-dumpy" way, please consider reading my fic Just As It Was. It's told through Sejanus's POV and is a Sejarcus fic, but the last half is set in D13 and dives into the character dynamics and specifics of all the people I mentioned in this post. Also I PROMISE I will update soon!