Any discussion of the Star League will inevitably focus on its ten major states, especially the four which fought to remain independent. But wouldn't there have been innumerable minor states too, who weren't as capable of resisting? We know colonization continued during the Star League - couldn't more have formed?
These questions are only partially addressed in the lore, and in only two places: MW1e (page 7) says there were six Territorial States when the Star League fell, and the first Periphery sourcebook (hereafter P1e) suggests six or seven such regions on its map of "geographic" zones.
Here's P1e's geographic map superimposed on its political map.
Four of the geographic zones match what the text says about the original size and extent of the Outworlds Alliance, Taurian Concordat, Magistracy of Canopus, and Rim Worlds Republic (née Rift Republic). That suggests the other zones correspond with Star League-era states too.
The "March Worlds" zone is especially interesting. It has the remains of the Alphard Trading Corporation, which dabbled in Periphery politics, produced 30 'Mechs/month for Amaris, and was decimated by Kerensky's forces (MW1e, p136); it has lots of remnant states, like the "Rift" and "Outer Sphere" zones do; and it overlaps the FWL's Rim Commonality province. I remember from HM:FWL that the FWL relied on foreign production for much of their war material, that the FWL was on better terms with the nearby Periphery than the other Star League Member-States were, and that the ruling Marik was sore at Kerensky around this time. I wonder if these things were related.
The "Capellan Marches" seem to contain New Vandenberg, which means it can't be a separate nation. But it could be the Taurian worlds which participated in the New Vandeberg Revolt. That'd be worth marking as a seventh zone.
The "Draconian Drift" would contain the final Territorial State. Never heard anything about it, not even by inference. But habitation there is so scarce, both on the map and in the text, that maybe silence isn't surprising.
Star's End is in the wrong place, incidentally. The texts of both MW1e and P1e agree that it should be mirrored over to the right, to put a lobe of the "Draconian Drift" between it and the Oberon Confederation. (For some reason the Steiner and Kurita maps put Porthos there instead, and Star's End where Porthos should be.)