The biggest Sartarite city – as described in the Dragon Pass book – is Boldhome, with over 10,000 residents. It is twice the population of the other cities around the Quivin Mountains put together, and perhaps it is best to think of the Kingdom of Sartar as Boldhome, its network of three satellite cities all linked together by roads, and its allied tribes. Each of the tribes are quasi-autonomous with their own petty kings and chiefs, but Boldhome has more people than any tribe except the Colymar (which explains their self-importance), and is far richer.
The second biggest Sartarite city is actually New Pavis, with almost 6,000 residents. It is actually significantly larger than Alda-Chur (with 4,000 residents, not counting the Lunar Army camp). Alda-Chur is linked to Sartar by road and tradition, but is still under Lunar occupation.
New Pavis is quite a long ways away. It is over 215 km as the hawk flies, and takes about 11-12 days to get from Boldhome to New Pavis, regardless of whether you take the north route or the south route. New Pavis is simply too far away to be more than an ally of Boldhome – unless you manage to have the Praxians as part of your alliance.
Now to put that in context, that’s about the length of the Mojave Road from the Colorado River to Los Angeles.