Inca Civilization
Article

Size of the Inca Empire at its greatest extent

At the height of its power in the early sixteenth century, the Inca Empire of Tawantinsuyu (“the Four Regions Together”) was the largest state ever to emerge in the pre-Columbian Americas. The empire stretched for roughly 4,000 kilometers along the Andean mountain chain, from the Ancasmayo river near the modern Colombia–Ecuador border in the north to the Río Maule in central Chile in the south. It included almost the entire length of the Andes and the adjacent Pacific coast, an area of perhaps 2,000,000 square kilometers — comparable in extent to the Roman Empire at its largest. The population of the empire is estimated by modern demographers to have been between roughly six and fourteen million people, with most estimates clustering around ten million. By any measure, the Inca Empire on the eve of the Spanish arrival was one of the largest polities in the world at that time. The geographic and demographic scale of the empire is the subject of this article; the institutional structures that made it governable are treated in the article on the history of the Inca Empire at its height.

Geographic Extent

The empire followed the line of the Andes from north to south, with extensions onto the Pacific coast and eastward into the cloud forest and the fringes of the Amazon basin. The northern boundary is generally fixed at the Ancasmayo river; the southern boundary was the Río Maule, where Inca armies were repulsed by the Mapuche. The empire thus spanned roughly 35 degrees of latitude, an extent comparable to the distance from London to the Sahara. The eastern boundary was the most fluid: the Antisuyu, the eastern suyu of the empire, included the eastern Andean slopes and adjacent lowlands, but Inca control of this region was always limited. The Amazonian peoples of the montaña — including groups speaking Jíbaro, Aguaruna, and many other languages — remained on the margins of the empire and were a constant source of frontier conflict. The Chachapoya of the cloud forest north of the Marañón, while eventually incorporated, retained a partly autonomous status.

The western boundary was the Pacific Ocean. The empire included almost the entire coast of modern Peru and northern Chile, a desert strip whose rivers sustained a string of irrigated agricultural valleys. Major Inca administrative centers such as Chan Chan, Nazca, and Arica were incorporated into the coastal system, while highland cities such as Cajamarca and Huánuco Pampa anchored the route between the coast and the mountains. The core of the empire was the central Andean highlands, especially the basin of Cusco, the Titicaca plateau, and the highland valleys of modern Peru. The major population centers were in the highlands, where altitude, water, and fertile valley soils supported dense agricultural populations. The lowland and coastal regions were integrated through a network of roads, garrisons, and storage facilities that allowed the state to extract surplus and to project power over very long distances.

The Four Suyus

The empire was divided into four large regions called suyus, each of which contained a number of provinces. The division is described in detail by the chronicler Pedro Cieza de León and is the basic geographic framework of the imperial administration. The four suyus were:

  • Chinchaysuyu, the northwestern region, extending from the Cusco valley north through the central highlands and into Ecuador and southern Colombia. It was the largest of the four suyus.
  • Antisuyu, the northeastern region, comprising the eastern Andean slopes and adjacent cloud forest and lowland. Inca control here was partial and treated as a frontier zone.
  • Collasuyu, the southwestern region, extending from the Cusco basin south through the Titicaca plateau and into Bolivia, northern Chile, and northwestern Argentina.
  • Contisuyu, the western region, including the western Andean slopes and the Pacific coast from central Peru to northern Chile.

The four suyus met at the capital, Cusco, which was understood as the ombligo del mundo — the navel of the world. From Cusco, four great roads radiated outward toward the four quarters, and the city’s plan was a microcosm of the imperial geography. The four regions of Tawantinsuyu are discussed in detail in the geography and administration section.

Population and Demography

The population of the Inca Empire is a subject of long-standing scholarly debate. The most thorough modern estimates are those of the demographic historian Henry F. Dobyns, who proposed a figure of 30 to 37 million people for the pre-Columbian Andes as a whole, of whom some 12 to 16 million would have been Inca subjects. More recent estimates, based on colonial-era tribute records and on regional archaeological surveys, have tended to be lower. The standard scholarly figure for the population of Tawantinsuyu on the eve of the Spanish conquest is in the range of 10 million, with a margin of uncertainty of perhaps 30 percent in either direction.

The population was concentrated in the highland basins and the irrigated coastal valleys. The basin of Cusco probably supported several hundred thousand; the Titicaca basin supported perhaps a million; and the densely settled coastal valleys of the central and north coast supported comparable numbers. The eastern lowlands were sparsely populated and contributed relatively little to the imperial total. The population of the empire was also very diverse: the Quechua-speaking peoples of the central highlands formed the core, but the empire included large populations of Aymara speakers in the south, Kichwa speakers in the north, and many smaller groups speaking languages now extinct. The imperial administration used a single system of provincial administration and a single legal framework across this diversity — a remarkable achievement of pre-modern governance.

The Imperial Infrastructure

The empire of this size could not have been governed without an extraordinary infrastructure of roads, storage, and administration. The most important element was the great road system, the Qhapaq Ñan (“Royal Road”), which ran the length of the Andes and connected all four suyus to the capital. The road system is treated in detail in the article on the Inca roads and the Qhapaq Ñan; its total length is estimated at 30,000 to 50,000 kilometers, including secondary and tertiary roads. The system allowed armies, messengers, and porters to move rapidly across the empire, and it enabled the administration to monitor conditions in distant provinces.

The storage network of the empire, organized around the state granaries known as qollqas, was equally important. The Incas built thousands of qollqas in provincial centers and along the road system, and they used them to store surplus agricultural production, textiles, and weapons. The state could draw on these stores to provision armies, to support populations during famine, and to reward collaborators. The storage facilities and the qollqa system are among the most distinctive features of the imperial infrastructure.

The administrative structure of the empire was built around a hierarchy of officials appointed by the Sapa Inca. The empire was divided into provinces each governed by an official of imperial rank, with sub-provinces governed by officials of lower rank, and so on down to the level of the ayllu. Census data, tribute assessments, and military obligations were recorded on the quipu, the knotted-cord device that served as the empire’s primary record-keeping technology. The combination of roads, storage, and the quipu system allowed a single political authority to govern a population of many millions across a vast territory.

A Continent-Sized State

The Inca Empire at its height was a continent-sized state that no European power of the same period could have matched in territorial extent per capita of ruling population. It was not a centralized bureaucratic state in the modern sense; it was a redistributive empire that worked through the existing structures of Andean society, layering Inca institutions on top of local ones. The result was a state that was simultaneously very old in its Andean roots and very new as a continental power. The empire that the Spanish encountered in 1532 had taken less than a century to reach its greatest extent, and it had done so by building on the institutional and cultural inheritance of older Andean states such as Tiwanaku and Wari. Its size was a measure of the success of this synthesis.