Which preposition to use with viceroyalties

of Occurrences 5%

Such framework of government as had been in existence was practically annihilated, and the various provinces of the late Viceroyalty of Buenos Ayres fell a prey to the military chieftains who could attract around them the largest number of Gaucho cavalry,while civilization, commerce, and every peaceful art, declined at a rapid rate.

at Occurrences 1%

Had he been in his old viceroyalty at Tientsin, this Boxer war could not have occurred.

Which preposition to use with  viceroyalties