There is perhaps historiographical irony in the fact that the majority of the very considerable literature that exists on the administration of Spanish colonial towns in the sixteenth and seventeenth centuries is in many respects disappointing precisely because authors have drawn heavily for their information on the most obvious of sources – the lihros de cabildo, or books of transactions of municipal councils. These volumes, which survive in appreciable numbers from an early date in many regions of Hispanic America, record faithfully every meeting of town councils, the number, names and offices of councilmen, their votes on many issues, their proposals and their executive orders in matters which they were competent to decide. The books, then, serve admirably as sources for the description of a cabildo's activities, and many such descriptions have been drawn from them by local and general historians of municipal life in the Spanish colonies. But precisely because they are official records, compiled by the town council's scribe, they draw a veil across dissension and dispute within the cabildos, hiding almost completely from view the play of interests of whose existence the historian is frequently aware from other sources. The local politics of colonial towns, in short, cannot be followed from the libros de cabildo, and other sources for them are so sporadic that any account must contain a large element of surmise. This is certainly true of Zacatecas, where most of the libros de cabildo for the period under study survive, with the exception of the first book, ending in 1586, and the fourth, covering the years 1639 to 1650.