The District Columbia is a unique feature in Medieval America. Located between the Cascade range and the rest of the Rocky Mountains, it's the only feudal state in the continent's west. It's also the only feudal state state which isn't Christian in denomination. There are no large cities in Columbia, but rather a group of estates and fortresses. The Columbian warlords hold a tight grip on the peasants, as there's on-stop war on every side.
The rivalry of the Pacific Northwest city-states were coming to fierce and bloody heads. The Buddhist priests convened, and in an attempt to create solidarity, declared Holy War on the Empire of Deseret, who's heathen kings had raped the land and showed no respect for the Earth. It was every Cascadian's duty to vanquish the Mormons. The elites would finance these wars, and once Deseret fell, people began setting up colonies. These fiefdoms were at times, a strange mishmash of cultures. They would include Lords with out of town estates, warrior-monks with their own garrisons, and even a few herdsmen who were converted to Buddhism and set up settled communities. Columbia was seen as the future of the continent. The Cascadia way of life and faith would expand further.
However, a hardened Deseret regained control of Snake River. Their hopes of establishing a new world order were vanquished, and Pacific Republics abandoned this new project and went right back to squabbling with one another. While its size was drastically reduced, the warlord estates which had been there for generations remained. Loyalties and chaos would likely have seen the new nation collapse, however the armies of warlord Aiden Lang were able to unify the populace into a single state.
Columbia's relationship with its coastal neighbors to the west is tense and complicated. On one hand, the merchant-cities see the District as a bunch of country bumpkins with swords. On the other, it makes a good buffer against the Mormons. For its part, the District of Columbia seas the the cities of Cascadia as a neglectful parent which needs new blood.