viewtopic.php?f=7&t=3071&p=67076&hilit=Barren#p67076
In Harchong, the Church and the local aristocracy have been joined at the hip to an even greater extent than elsewhere on the mainland. Harchong — or what eventually became the Harchong Empire, at least — was the focus of the early population and expansion of Safehold for several reasons, despite the fact (if you look at the map) that its internal communications are relatively poor. Tiegelkamp, Boisseau, Stene, Kyznetzov, and Shwei were primarily grassland and particularly fertile. They required much less in the way of terraforming and land clearance, which made them the heart of Haven's early population growth. The emergence of a strong dynasty in Tiegelkamp which succeeded in uniting all of those separate enclaves into provinces of the same name into Safehold's first true empire during the War of the Fallen — and which put its new, imperial strength behind Langhorne's successors — explains a lot about both Harchong's size and power and its "special relationship" with the Church and with the forces of doctrinal reliability, in particular.
That's a mix of North and South Harchong provinces about the Gulf of Dohlar. It upsets the forum theory that Harchong originated in Horth Harchong and later assimilated/conquered South Harchong. It turns out that it was an amalgamation of enclaves around the northern and southern coasts of the western end of the Gulf of Dohlar. Think of it like the Roman Empire based around the Mediterranean as its central communications net, but without including the Mediterranean/Gulf of Dohlar's eastern shores. From there, the Empire expanded inland on both continents. I take suspect that expansion was into places without well-developed enclaves, and that the eastern Gulf had targets that, between themselves and the Church, weren't especially open to Harchongese assimilation.
I haven't yet found any other reference to Boisseau, so that's a new question.