Under Augustus, Roman provinces were split into two groups. Senatorial provinces were quieter regions, governed by men chosen by the Senate. Imperial provinces were the frontier regions with most of the army, governed by men chosen by the emperor.
Key takeaways
- Imperial provinces held most of the army: in 27 BC they contained 22 of the 28 legions [1].
- Senatorial governors were proconsuls who normally served one year, while imperial governors usually served several [1].
- Africa Proconsularis, a senatorial province, covers 289,538 km² on the map and was annexed in 146 BC.
- The map draws 43 province outlines but does not mark which kind each one was.
How the two kinds of province worked
When Augustus took power in 27 BC, the Senate gave him the title Augustus and made him princeps, with proconsular power [2]. In the same settlement the provinces were divided between him and the Senate. The idea was to keep up the look of the old Republic while putting the soldiers in his hands.
Imperial provinces were the ones that needed an army: the frontier regions and the unsettled ones. They belonged to the emperor, but were governed by legates, officers who acted for him [2]. The formal title was legatus Augusti pro praetore, and Augustus could replace a legate whenever he liked [1]. These governors usually stayed in post for several years [1]. In 27 BC these provinces contained 22 of the 28 legions, over 80 per cent of the army [1].
Senatorial provinces were older, quieter regions. Their governors were proconsuls chosen by lot each year [2], and they normally served only one year [1]. The most desirable ones, Africa and Asia, went only to former consuls [1]. Few of these provinces kept any troops: after Augustus's wars in the Balkans, only Africa still kept a legion [1].
Egypt was a special case. It was ruled by a prefect of the knightly class, a lower social rank than a senator, and treated as the emperor's own property [1].
The system was never fixed. Emperors added new provinces, and the practical power of the emperor over all of them grew.
An example from our data
Africa Proconsularis shows the senatorial type. Its outline on our map covers 289,538 km², with its capital at Carthago. It was annexed in 146 BC and lost in AD 439, and covers Libya and Tunisia today.
For the imperial type, look at Britannia, annexed in AD 43, a frontier province held by legions, and so an imperial one. And Aegyptus, annexed in 30 BC, covers 494,488 km² on the map and was ruled by a prefect [1].
On the map, set the date to AD 14, the year Augustus died, and switch on the Provinces layer: it shows 36 provinces held. The layer does not mark which kind each one was, so use the province pages and the sources below to check. The homepage explains the controls.
The thing people get wrong
Many people imagine that the Senate really governed its provinces independently. On paper the proconsuls had separate commands [1], but the emperor held the army, had the larger share of the empire, and controlled the Senate in practice [2]. A senatorial province was a place where the emperor chose not to station an army, not a place free of him.
The other popular mistake is to say senatorial provinces were richer or more important. Africa and Asia were prestigious and wealthy, but the imperial provinces held the soldiers, and so the power.
Imperial vs senatorial
| Imperial province | Senatorial province | |
|---|---|---|
| Who chose the governor | The emperor | The Senate, by lot each year |
| Governor's title | Legate | Proconsul |
| Usual length of service | Several years | About one year |
| Army | Most of the legions | Little or none |
Frequently asked questions
Which provinces were senatorial?
The best known were Africa and Asia, which were given only to former consuls. Quieter regions with no need for an army were the usual choice for the Senate's share.
Was Egypt imperial or senatorial?
Neither in the usual sense. It was ruled by a prefect from the knightly class, appointed by the emperor, and treated almost as his personal property.
Can the map show imperial and senatorial provinces?
No. The province layer shows outlines and facts such as capitals and dates, but not which kind of governor each province had.
Sources
- Roman province, Wikipedia.
- Roman Empire, Wikipedia.
- Every figure from our own map is worked out from the datasets on the data sources page (checked against Ancient World Mapping Center outlines and Pleiades).