Spiro Mounds, near the modern town of Spiro in eastern Oklahoma, is the site of a series of twelve earthen burial mounds associated with the Mississippian tradition of the Mound Builders, who begin constructing mounds there in about 1000.

Inhabited from 850, Spiro is the westernmost outpost of the Mississippian culture that has spread along the lower Mississippi drainage area and its tributaries.

The vast Mississippian trading network brings obsidian from Mexico, colored flint from New Mexico, copper from the Great Lakes, mica from the Carolinas, and conch shells from the Gulf Coast.

The engravings of humans, animals, and geometric designs on the conch shells at Spiro are particularly well rendered and undoubtedly had profound symbolic significance.

The Spiro's ceremonial objects are some of the most sophisticated artforms ever found in the Mississippian region.

The artistic skills and earthwork mound-building of the Caddoan Mississippians flourish during the twelfth and thirteenth centuries.

The Spiro Mounds, near the Arkansas River in present-day southeastern Oklahoma, are some of the most elaborate mounds in the United States.

They are made by Mississippian ancestors of the historic Caddo and Wichita tribes, in what is considered the westernmost point of the Mississippian culture.

The Caddo are farmers and enjoy good growing conditions most of the time.

The Piney Woods, the geographic area where they live, is affected by the Great Drought from 1276–1299 CE, which covers an area extending to present-day California and disrupts many Native American cultures.

Archeological evidence has confirmed that the cultural continuity is unbroken from prehistory to the present among these peoples.

The Caddoan Mississippian people are the direct ancestors of the historic Caddo people and related Caddo-language speakers who will encounter the first Europeans, as well as of the modern Caddo Nation of Oklahoma.

A rapid decline of the so-called Mississippian societies of fortified towns and smaller villages, farmsteads, and hunting and gathering sites strung along the Mississippi Valley and its major tributaries occurs at he beginning of the fifteenth century.

The Late Mississippian period, usually considered from about 1400 to European contact, will be characterized by increasing warfare, political turmoil, and population movement.

Some of the Caddo territory had been invaded by migrating Dhegihan-speaking peoples, Osage, Ponca, Omaha, and Kaw, who moved west beginning about 1200 due to years of warfare with the Iroquois in the Ohio River area of present-day Kentucky.

The Iroquois had taken control of hunting grounds in the area.

The Osage particularly had fought the Caddo, competed for territory, and become dominant in the region of present-day Missouri, Arkansas, and eastern Kansas.

These tribes had become settled in their new territory west of the Mississippi prior to mid-eighteenth-century European contact.

Most of the Caddo historically live in the Piney Woods ecoregion of the United States, divided among the state regions of East Texas, southern Arkansas, western Louisiana, and southeastern Oklahoma.

This region extends up to the foothills of the Ozarks.

The Piney Woods are a dense forest of deciduous and pinophyta flora covering rolling hills, steep river valleys, and intermittent wetlands called "bayous".

Caddo people primarily settle throughout the river valleys of East Texas and adjacent regions.

When they first encounter Europeans and Africans, the Caddo tribes organize themselves in three confederacies: the Natchitoches, Hasinai, and Kadohadacho.

They are loosely affiliated with other neighboring tribes including the Yowani, a Choctaw band.

The Natchitoches live in now northern Louisiana, the Hasinai live in East Texas, and the Kadohadacho live near the border of Texas, Oklahoma, and Arkansas.

The Caddo people have a diet based on cultivated crops, particularly maize (corn), but also sunflower, pumpkins, and squash.

These foods hold cultural significance, as do wild turkeys.

They also hunt and gather wild plants.