hickory logs. The wall was about 12 feet (3.6 meters) high, with projecting bastions every 70 feet (21 meters) along its length. Outside it, thousands of single-family houses clustered, organized in small groups around ceremonial poles. Although it may have served as a social barrier between the Cahokian elite and the general population, it is clear from its form and the evidence of some hastily built parts that the palisade’s main purpose was defense. It was rebuilt three times before 1300.

The inner city of Cahokia was dominated by an enormous platform mound, identified as the largest prehistoric earthwork in the Americas. Surviving today, Monks Mound was named after a Trappist monastery in the vicinity. Its base, measuring 1,037 by 790 feet (291 by 236 meters), extends over 14 acres (5.25 hectares), and the structure rises through four sloping-sided rectangular terraces to a height of 100 feet (30.6 meters). It contains 820,000 cubic yards (692,000 cubic meters) of earth, all of which was hand-excavated from large “borrow” pits and carried in woven baskets to the site. Monks Mound was built in several stages over about 200 years, with carefully designed strata of sand and clay, and drains to deal with water saturation. Long ago, it was crowned with a 50-foot-high (15-meter) thatched-roof building of timber-pole construction, 105 by 48 feet (31 by 14 meters). Some scholars identify it as a temple. It was certainly the chief’s residence, in which the political and religious observances were conducted that ensured the nation’s continuing prosperity. In effect, the mound was a means of lifting Mother Earth to Father Sky, bringing male and female together. That these ancient builders could set out their city with its streets aligned to the cardinal compass points and construct such a durable monument over generations, without having a written language or the wheel, makes their accomplishment the more marvelous.

Around 1200, for reasons that may only be guessed, Cahokia began to decline. Perhaps growth had placed too much burden upon the agricultural hinterland or overloaded the urban infrastructure; perhaps deforestation had changed the local ecology. Or perhaps there was civil war over dwindling resources. Other scholars attribute the demise of the city to a mud slide on the great mound, which may have been construed as an omen. No one really knows. And no one knows where the Cahokians went. By 1400 their remarkable metropolis was abandoned. Arriving much later in the area, the first Europeans mistook the mounds, overgrown by then, for natural hillocks. Monks Mound was not discovered until the beginning of the nineteenth century.

Modern farming, expanding towns, highways, and pollution continue to threaten those smaller communities around Cahokia that have not already been destroyed. The 2,200-acre (890-hectare) Cahokia Mounds State Historic Site is administered by the Illinois Historic Preservation Agency. It was added to UNESCO’s World Heritage List in 1982. Archeological investigation continues. Following major slumps on the east and west sides of Monks Mound in the mid-1980s, attempts were made to reduce internal waterlogging. In January 1998 construction workers, drilling horizontally into the west side, struck a deep layer of limestone or sandstone cobbles 40 feet (12 meters) beneath the surface. Further tests were hampered by groundwater, but the find has excited scientists because stone does not naturally occur in the region. There is much more to be revealed at Cahokia.

Further reading

Pauketat, Timothy R., and Thomas E. Emerson, eds. 1997. Cahokia: Domination and Ideology in the Mississippian World. Lincoln: University of Nebraska Press.

Young, Biloine Whiting, and Melvin L. Fowler. 1999. Cahokia, the Great Native American Metropolis. Champaign: University of Illinois Press.

Canal system

England

The creation of England’s inland water-transport network during the 1700s was among the most important contributors to the Industrial Revolution. In the second half of the century, manufacturing, already transformed by entrepreneurial labor management, was shifting from cottage industry to factories, where machines mass-produced goods. A cheap, efficient transport infrastructure was vital to gather raw materials and distribute products. Because