The Mississippian culture was a Native American civilization that flourished in what is now the Midwestern, Eastern, and Southeastern United States from approximately 800 to 1600, varying regionally. It was known for building large, earthen platform mounds, and often other shaped mounds as well.   It was composed of a series of urban settlements and satellite villages linked together by loose trading networks.  The largest city was Cahokia, believed to be a major religious center located in what is present-day southern Illinois.
The Mississippian way of life began to develop in the Mississippi River Valley (for which it is named). Cultures in the tributary Tennessee River Valley may have also begun to develop Mississippian characteristics at this point. Almost all dated Mississippian sites predate 1539–1540 (when Hernando de Soto explored the area),  with notable exceptions being Natchez communities. These maintained Mississippian cultural practices into the 18th century. 
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A number of cultural traits are recognized as being characteristic of the Mississippians. Although not all Mississippian peoples practiced all of the following activities, they were distinct from their ancestors in the adoption of some or all of these traits.
The Mississippians had no writing system or stone architecture. They worked naturally occurring metal deposits, such as hammering and annealing copper for ritual objects such as Mississippian copper plates and other decorations,  but did not smelt iron or practice bronze metallurgy.
The Mississippian stage is usually divided into three or more chronological periods. Each period is an arbitrary historical distinction varying regionally. At a particular site, each period may be considered to begin earlier or later, depending on the speed of adoption or development of given Mississippian traits. The "Mississippian period" should not be confused with the "Mississippian culture". The Mississippian period is the chronological stage, while Mississippian culture refers to the cultural similarities that characterize this society.
The term Middle Mississippian is also used to describe the core of the classic Mississippian culture area. This area covers the central Mississippi River Valley, the lower Ohio River Valley, and most of the Mid-South area, including western and central Kentucky, western Tennessee, and northern Alabama and Mississippi. Sites in this area often contain large ceremonial platform mounds, residential complexes and are often encircled by earthen ditches and ramparts or palisades. 
Middle Mississippian cultures, especially the Cahokia polity located near East St. Louis, Illinois, were very influential on neighboring societies. High-status artifacts, including stone statuary and elite pottery associated with Cahokia, have been found far outside of the Middle Mississippian area. These items, especially the pottery, were also copied by local artists.
The term South Appalachian Province was originally used by W. H. Holmes in 1903 to describe a regional ceramic style in the southeast involving surface decorations applied with a carved wooden paddle. By the late 1960s, archaeological investigations had shown the similarity of the culture that produced the pottery and the midwestern Mississippian pattern defined in 1937 by the Midwestern Taxonomic System.
In 1967, James B. Griffin coined South Appalachian Mississippian to describe the evolving understanding of the peoples of the Southeast.  South Appalachian Mississippian area sites are distributed across a contiguous area including Alabama, Georgia, northern Florida, South Carolina, central and western North Carolina, and Tennessee. Chronologically this area became influenced by Mississippian culture later than the Middle Mississippian area (about 1000 as compared to 800) to its northwest. It is believed that the peoples of this area adopted Mississippian traits from their northwestern neighbors. 
Typical settlements were located on riverine floodplains and included villages with defensive palisades enclosing platform mounds and residential areas.  Etowah and Ocmulgee in Georgia are both prominent examples of major South Appalachian Mississippian settlements. Both include multiple large earthwork mounds serving a variety of functions.
Villages with single platform mounds were more typical of the river valley settlements throughout the mountainous area of southwest North and South Carolina, and southeastern Tennessee that were known as the historic Cherokee homelands. In Western North Carolina for example; some 50 such mound sites in the eleven westernmost counties have been identified since the late 20th century, following increased research in this area of the Cherokee homeland. 
The Caddoan Mississippian area, a regional variant of the Mississippian culture, covered a large territory, including what is now eastern Oklahoma, western Arkansas, northeastern Texas, and northwestern Louisiana. Archaeological evidence has led to a scholarly consensus that the cultural continuity is unbroken from prehistory to the present, and that the Caddo and related Caddo language speakers in prehistoric times and at first European contact are the direct ancestors of the modern Caddo Nation of Oklahoma. 
The climate in this area was drier than areas in the eastern woodlands, hindering maize production, and the lower population on the plains to the west may have meant fewer neighboring competing chiefdoms to contend with. Major sites such as Spiro and the Battle Mound Site are in the Arkansas River and Red River Valleys, the largest and most fertile of the waterways in the Caddoan region, where maize agriculture would have been the most productive.  The sites generally lacked wooden palisade fortifications often found in the major Middle Mississippian towns. Living on the western edge of the Mississippian world, the Caddoans may have faced fewer military threats from their neighbors. Their societies may also have had a somewhat lower level of social stratification.
The Caddoan people were speakers of one of the many Caddoan languages.  These languages once had a broad geographic distribution, but many are now extinct. The modern languages in the Caddoan family include Caddo and Pawnee.
Hernando de Soto led an expedition into the area in the early 1540s, he encountered several native groups now thought to have been Caddoan. Composed of many tribes, the Caddo were organized into three confederacies, the Hasinai, Kadohadacho, and Natchitoches, which were all linked by their similar languages.
The Plaquemine culture was an archaeological culture in the lower Mississippi River Valley in western Mississippi and eastern Louisiana. Good examples of this culture are the Medora site (the type site for the culture and period) in West Baton Rouge Parish, Louisiana, and the Anna, Emerald Mound, Winterville and Holly Bluff sites located in Mississippi.  Plaquemine culture was contemporaneous with the Middle Mississippian culture at the Cahokia site near St. Louis, Missouri. It is considered ancestral to the Natchez and Taensa Peoples. 
Although the Mississippian culture was heavily disrupted before a complete understanding of the political landscape was written down, many Mississippian political bodies were documented and others have been discovered by research.
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Mississippian peoples were ancestral to the majority of the American Indian nations living in this region when European trade began.  The historic and modern day American Indian nations believed to have descended from the overarching Mississippian culture include: the Alabama, Apalachee, Arikara, Caddo, Chickasaw,  Catawba,[ citation needed] Choctaw,  Muscogee Creek, Guale, Hitchiti, Ho-Chunk,[ citation needed] Houma, Iowa,[ citation needed] Kansa, Koroas,  Missouria, Mobilian, Natchez,  Omaha, Osage (possibly),  Otoe,[ citation needed] Pawnee, Ponca,[ citation needed] Quapaw (possibly),  Seminole (broad origins),  Taensas,  Tunicas,  Yamasee, Yazoos,  and Yuchi.[ citation needed]
Scholars have studied the records of Hernando de Soto's expedition of 1539–1543 to learn of his contacts with Mississippians, as he traveled through their villages of the Southeast. He visited many villages, in some cases staying for a month or longer. The list of sites and peoples visited by the Hernando de Soto Expedition chronicles those villages. Some encounters were violent, while others were relatively peaceful. In some cases, de Soto seems to have been used as a tool or ally in long-standing native feuds. In one example, de Soto negotiated a truce between the Pacaha and the Casqui.
De Soto's later encounters left about half of the Spaniards and perhaps many hundreds of Native Americans dead. The chronicles of de Soto are among the first documents written about Mississippian peoples and are an invaluable source of information on their cultural practices. The chronicles of the Narváez expedition were written before the de Soto expedition; the Narváez expedition informed the Court of de Soto about the New World.
After the destruction and flight of the de Soto expedition, the Mississippian peoples continued their way of life with little direct European influence. Indirectly, however, European introductions dramatically changed these native societies. Because the natives lacked immunity to infectious diseases unknowingly carried by the Europeans, such as measles and smallpox, epidemics caused so many fatalities that they undermined the social order of many chiefdoms. Some groups adopted European horses and changed to nomadism.  Political structures collapsed in many places.
At Joara, near Morganton, North Carolina, Native Americans of the Mississippian culture interacted with Spanish colonizers of the Juan Pardo expedition, who built a base there in 1567 called Fort San Juan. Expedition documentation and archaeological evidence of the fort and Native American culture both exist. The soldiers were at the fort about 18 months (1567–1568) before the natives killed them and destroyed the fort. (They killed soldiers stationed at five other forts as well; only one man of 120 survived.) Sixteenth-century Spanish artifacts have been recovered from the site, marking the first European colonization in the interior of what became the United States. 
By the time more documentary accounts were being written, the Mississippian way of life had changed irrevocably. Some groups maintained an oral tradition link to their mound-building past, such as the late 19th-century Cherokee.  Other Native American groups, having migrated many hundreds of miles and lost their elders to diseases, did not know their ancestors had built the mounds dotting the landscape. This contributed to the myth of the Mound Builders as a people distinct from Native Americans, which was rigorously debunked by Cyrus Thomas in 1894.