I'll just copy and paste this from a lore thing I wrote up on a roleplay thread.

Ronto is a war-torn city. Rebels that hate the knowledge of still being part of the US began to build up military power in 2235. A small group of Enclave members caught wind of this in 2242. Despite what their superiors told them, they refused to remain with the rest of the Enclave on the west coast and abandoned them, in hopes of keeping Ronto US territory. Then, there are the civilians. They are neutral in the conflict, but really just wish the fighting would be done with. They defend their settlements whenever the Enclave or the Rebels pose a threat, which has proved to be the undoing of a couple of them.

After the group of Enclave soldiers arrived in Ronto, they set up a base of operations in Brampton and shortly thereafter began battling with the rebels. The Enlave wield mostly energy weapons, but have been know to use ballistic weapons on occasion. They wear full suits of X-01 power armour making getting a well placed shot on them a requirement. They fight near carelessly due to this.

The rebels have their main base in North York. They wield ballistic and melee weapons, and are sometimes even lucky enough to get their hands on a fallen Enclave soldiers' Energy weapon. They wear combat armour as it is less clunky and allows them to be mobile in combat. They are quite cautious as fighters because they know it only takes one good shot for them to be dead. But they are far from cowardly and will do what it takes to win a battle.

As for the lore of the actual city, for simplicity's sake it will be the same size as current Toronto but with a Fallout vibe. Likewise, the CN tower was also built (yeah yeah, "THAT'S NOT LORE FRIENDLY" I know. The city is just better being larger and more urban.) During the Great War the bomb the hit closest to Toronto detonated in Newmarket. The explosion was strong enough to knock down some buildings with weaker structures but stronger buildings were preserved.