This thread is still largely a brainstorming exercise but I wanted to share some of my ideas that I have so far. Sorry if it is a bit word intensive!
So the history of my landmass will be very similar to that of Chumpy's 54, being in the same region. Chumpy did not include any time frames within his thread so I am going to assume that it was not a fast process, helping to explain how Phase 2c occurred so 'fast'.
Phase 1: Wilds
Initially this area 57 was ruled by the giants in the Northwest corner and the rest of the area was 'uncivilized' (goblins are a possible fill in race here... I might change this to something else depending on climate etc.).
Phase 1.jpg
Phase 2: Migration Period (same as Chumpy's phase 1-3)
a. initial settlement along the coast
Phase 2a.jpg
b. conquering coasts and southern boundaries of the 'Hardstamp 'Republic'' (best translation available for the Giant nation)
Phase 2b.jpg
c. The human migrants subjugate the entire region, overrunning the giants in the north and the goblins to the south, gaining control of the entire region (Coincides with Chumpy's phase 3 until around halfway through Chumpy's 4).
Phase 2c.jpg
Phase 3: Collapse of the Human Nation (End of Chumpy's 4 into my timeline):
The giants, being threatened on all fronts, made a last desperate attack against the humans that were encircling them. Allying with the Goblins that the humans in area 57 subjugated, they manage to destroy the human's defenses (The humans being too spread out from conquering more than their population could control). Together these two races decimate the humans, forcing them to retreat both north and south to the coasts. The humans in the north stop the attack (at the X) by defeating Argulg in the Battle of _____. The humans who retreated south use the river as a defense against the giants and manage to hold their ground, defending their ports. They also manage to hold the goblins within the mountains to the South and the plains (or forests) in the central regions.
Phase 3.jpg
Phase 4: Stabilization
The borders stabilize. The Giants have conquered the area to the Northwest, controlling that whole territory up into the mountains. The goblins 'control' the central lands and mountains to the southeast. Though they do not have a single united nation, their warbands are exceptionally ferocious and manage to withstand human advances. The largest of the warbands is (at least the best translation) 'The Magnificant Dynasty of King Barg the Wonderful' - A lot is revealed of King Barg's personality in this title...
The Humans are restricted to the North and Southern coasts. Those in the north have access to the mountains & ores within, as well as, the flatter land around. Their section of coast is also part of the body of water above connecting many of the other map parts, so I imagine is a very well traveled area (especially with the straights right around the corner).
The humans in the south are have less mineral resources and are reliant on the goods they produce.
Phase 4.jpg
History ranting done (for now!). Let me know what you think!
I need to look a lot more about the actual climate of the region to help determine the possible goods, culture, etc. of the area (it is also needed for the mapping!).
Finally, if anyone knows one of the other countries nearby that possibly could have been the source of the migrants to my area that would help inspire the culture of my land, that would be great.