Portus owed its origin to two political decisions taken more than half a century apart, by the emperors Claudius and Trajan. Claudius faced a dire food shortage at the beginning of his reign, in AD 41. Seven or eight days' supply of grain was all that remained in the warehouses (Seneca, de brev. vit. 18.5; see Suet. Div. Claud. 18.2, 20.1; Dio. 60.11.3; see Garnsey, 1988: 222-223). Claudius' long-term response to the emergency was to set in motion, in the following year, the construction of a sea harbour in a lagoon that lay to the north of the mouth of the Tiber. His plan was to improve on Ostia, a river port, which did not permit anchorage in all weather and seasons.
The harbour was connected to the river by canals, as an inscription records (CIL XIV 85). It took more than two decades (and another emperor) to complete (AD 42-64?), and did not, in any event, create a safe haven for ships (Tac. Ann. 15.18). Trajan later completed the job in the early years of the second century (AD 100/6?-112) by building a hexagonal inner basin linked by a channel to the Claudian harbour, with an additional canal, the fossa Traiana ('canale di Fiumicino'), linking the now double harbour to the river Tiber (Testaguzza, 1964, 1970). The area of the complex of basins and canals was thereby extended to around 1,300,000 square meters. The basic, extensive engineering work must have been hugely expensive, and the varied architectural features and sculptural adornments (see Meiggs, 1973) confirm that these emperors were not interested in saving denarii.
Portus was the port of Rome, and the uninhibited flow of goods into the metropolis, first and foremost grain, but also other vital foodstuffs, was the highest priority of the imperial government. The prosperity of Portus was tied up with that of the imperial city. When Rome became a smaller and less important place, one consequence was that Portus had to struggle to survive against economic decline and the relentless advance of silt.
Portus in our period was not an independent municipium or colonia, as was Ostia. Whether or not it was officially a dependency of Ostia is unclear: in practice it was controlled by imperial officials. An inscription of AD 224 at Portus indicates who was in charge and shows an important and no doubt prestigious group of traders working with them (Thylander, 1951-52: B324, CIL XIV 125): 'The station of grain merchants have set up this plaque to the emperor Caesar Marcus Aurelius Severus Alexander Felix Augustus and to Iulia Mamaea, mother of our Lord and of the camp. The place was assigned to them by Agrigola, freedman of the emperor and procurator of the two ports, by Petronius Maximus, centurion of the grain supply, and by Fabius Maro, centurion for public works. It was dedicated on 3rd August under the consulship of Appius Claudius Iulianus and Bruttius Crispinus. The patron of the company Quintus Turranius Masila, Publius Flavius Felix Iunior, son of Flavius, and Valerius Donatus acted as supervisors'.
Portus, then, was a peculiar place, hardly a representative ancient Italian, or Graeco-Roman city, which does not mean of course that it is uninteresting. It does mean, among other things, that the character of the population is likely to have been unusual or unique, and this will be true also of the population of its cemetery, Isola Sacra, located between the river Tiber and the 'canale di Fiumicino', just off the road between Portus and Ostia.
The necropolis (Calza, 1940; Baldassarre, 1984, 1987; Pellegrino, 1984) belongs to the period when Portus was in its prime, the second century and early third, before Christianity had made a significant impact on the city, and certainly before a bishop was installed and the city given municipal status under Constantine.
What kind of people were buried (or in about one out of ten cases, cremated) at Isola Sacra? What kind of people lived or were active in Portus? At this cemetery, the graves speak. Their occupants, many of them - or, more precisely, those who set up or had had set up for them a 'tomba a camera' or a 'tomba a cassone' - have left inscriptions, occasionally embellished with a bas-relief, revealing names, family groups - including freedmen and freedwomen, and sometimes slaves - and from time to time, occupation. They are, it would seem, men of commerce and business, frequently themselves descended from slaves, and advertising, when they can, newly founded families, but also the erosion of such families by premature death, and the inevitable passing on to dependent freedmen and clients of an inheritance.
The cemetery population, as suggested by the tombs, is not homogeneous: a 'tomba a camera' required a far larger outlay than the more modest, but still typically inscribed, 'tombe a cassone', and there are anonymous 'tombe dei poveri' of various styles (Angelucci et al., 1990).
We could say that the population, those sections of it that are 'visible', was, or appears, relatively egalitarian, in comparison with other Italian towns. There is a missing 'tranche' in the social hierarchy, at the top, where one would expect to locate an aristocracy of office and social prestige.
When we cross the fossa Traiana to Portus itself and survey the surviving inscriptions, the picture changes a little, but not significantly. We now encounter a few imperial procurators who are usually freedmen of the emperor, one or two people who claim equestrian status but name no equestrian office, some army officers, and a handful of priests or priestesses. The only people who advertise a political career turn out to have pursued it at Ostia (Pavolini, 1983, 1986). It seems that there was no 'political class' at Portus, and therefore no conventional elite whose status, power and wealth stemmed from their formal leadership of the community. It was presumably the 'middle-class' of traders and craftsmen of the 'tombe a camera' of Isola Sacra who constituted the 'robur' or 'engine-room' of the town of Portus, if not its leadership.
