I got interested in the origin and continuity of european political subregions like duchies and counties, which lands one in the early middle ages and feudalism. Clicking further back into the carolingian and merovingian times (in Wikipedia) information is more scarce.
WP tells me, in the late Roman Empire since Diocletian there were small districts called pagi (pagus), administered by bureaucrats called comes. The Francs later kept the structure and the comes, well at least the title, later then feudalism and heritability. Do wo know what frankish pagi/counties where there and who ruled them? Or is there a lack of sources?
If not, are there any good resources to learn more about this early period? Maybe a good historical atlas?
In addition to this answer on Merovingian administration, we could add this on the countal figure in Merovingian and Carolingian Gaul.
With the collapse of public service in Northern Gaul, the function of grafio seems to have been an ad-hoc substitute for the "count of the pagus", holding important fiscal and legal authority on behalf of the king, seconded by centenari (possibly re-branded centuriones) and sacebaroni.
What the pagus he managed was is difficult to answer : it was traditionally held that medieval pagi and religious dioceses were essentially identical to the late Roman pagi and even to Gaulish pagi, but this idea is strongly criticized : most of the geographical mentions we have (which aren't much) don't really fit. The countal jurisdiction was already ill-defined in the Vth century, with the collapse of imperial authority in Gaul with the title being more than often likely self-awarded and more representative of a continued tradition of public service as a part of social class identity rather than public service in itself. As such "counts of the city" began to appear whose title and theoritical responsability was set on a place rather than a territory, which ambiguity might have well served the ambitions of the hour.
With the conquest of southern Gaul, Merovingian gained access not only to new wealth from confiscation of ager publicus and fiscal revenues of a fairly wealthy region, but also a renewed administrative model. Indeed, Goths and Burgundians established, trough legal codes, a palatial and local administrative system from which counts could be either at direct royal service (hence, "palatial counts") or direct royal agents locally: their jurisdiction weren't well defined, altough Burgundians made a distinction between "counts of the city" and "counts of the pagus" we're not really aware of the details, but as conveyors of the palace's need and authority.
Out of this models, Merovingians were able to found by the mid-VIth century a reborn public service (rather than directly conveying the late imperial administration) along the Theodosian models. Counts, which reappeared at this point in Merovingian Gaul, followed a similar model : being trusted with judicial and fiscal matters, but also with keeping order and answering to military call, a fusion of civilian and military powers that was foreign to the Late Empire (but arguably not of the post-Imperial states after 500 CE, including the Eastern Roman Empire). Their jurisdiction remains obscure, possibly because they could be still more or less easily removed or trusted with more responsabilities (including on other pagi and/or cities). In the same time, however, these counts had to share some effective power with the bishops that went trogugh a partial "bureaucratisation" and "aristocratisation" with a more or less official say or even jurisdiction over minor affairs, reinforced by a growing participation of bishops onto palatial administration.
This administration was still essentially Roman in shape (even if an evolution from it, on the poorer and relatively unsable grounds of the early Medieval era) and counts as royal agents were still dismissable, had to gather regularily to the palace to account for their measures and take guidelines from the king, etc. But on the same time they were often from the region they overseen and part of important aristocratic networks (altough not systematically), altough it didn't impact much the relative (and truth to be told, partly incidental) efficience of Merovingian bureaucracy whose golden age could be set on the mid-to-late VIth century up to the early-to-mid-VIIth century : the king was still able to move people out of their function (the turnover being somewhat important), could pay them with the fiscal revenues (both monetary but increasingly out of landed revenues from "loaned" public fisc).
This system was essentially existing only in Gaul, however : in spite of their power, Merovingian kings never managed (or even tried) to export it in their "inner" or "outer" sphere of influence (respectively in Germania and Britain) as it relied on a pre-existing social culture of writing and administration which was essentially Roman. You wouldn't have found Merovingian counts in Bavaria, Kent or even Franconia, something that became relevant eventually.
Indeed, the Merovingian realm went trough the consequences of the royal faida (i.e. the mix of hot and cold civil war that took place in the late VIth to early VIIth centuries), which could be described as a decline of old aristocratic families with many of them seemingly disappearing, and the rise of aristocracy as a power of its own. While the effects were held for a time during the reigns of Clothar II and Dagobert I, due to their reinforcement of royal authority, several concomitent and related evolutions took place and took precedence by the mid-to-late VIIth century : regionalisation of mandate (where Late Roman Empire barely tolerated naming servants in their region of origin), growing irrevocability, hereditary transmission of titles (which went together with whole families being considered as "noble" instead of the function and individuals), perenisation of fiscal grants (partly due to the pauperisation of royal court and demonetarisation of palatial economy), etc.
In the same time, as with other agents, counts were rivalled by the growingly important episcopalian function which was more and more trusted with formerly "lay" tasks including count's to the point some counts were also bishops, making them sometimes redundant. This rivality wasn't immediatly nocive for royal power (who found in religious elites a somewhat more legitim and trustworthy belt) but made the countal office less interesting in the same time bishops entierely partook in the aristocratic networks they belonged to; in the same time, the appearance of "semi-private" agents named officially by the aristocratic elites in their demesnes effectively rivaled with the "rural counts"'s position.
[partly taken from this answer]
Thus, a family or a set of families that threatened to control too much of public power locally was fought against by others (with royal arbitrage), but these often ambitioned to do that for themselves, which was as true for lay aristocrracy than ecclesiastical power (which might have both modelled and legitimized the former. Capacities of the royal fisc with endless and unrecoverable donations being increasingly strained, charges and revenues became a matter of local powers whose legitimacy came mostly from their landed and military role.
Public service and functions as counts were thus loosing attractivity compared to the new forms of power elites adopted, to the point being fairly marginal and empty, except as titling power of new autonomous or even effectively independent powers (first from the periphery as in Bavaria or Thuringia, then Aquitaine, Provence, eventually e.g. Alsace or Maine)
Carolingians did attept to reform a new public service out of the ashes, but had to rely on aristocratic families who were wholly associated with it, confusing the distinction between function and nobility : a Carolingian count did owned legitimacy to his relation with the king/emperor but didn't owed its social role and power to him. Henceforth, the capacity of the Carolingians to override local power was limited and more about negociation than coercition. Eventually what remained of late ancient public service entierely collapsed in the late IXth century, our of sheer exhaustion and political irrelevance.