River by the US federal government, as European-American settlers pushed the government to acquire their lands. Some members of the tribes chose to stay in their homelands and accept state and US citizenship; others simply hid in the mountains or swamps and sought to maintain some cultural continuity. Since the late 20th century, descendants of these people have organized as tribes; in a limited number of cases, some have achieved federal recognition but more have gained state recognition through legislation at the state level. Culture Frank Speck identified several key cultural traits of Southeastern Woodlands peoples. Social traits included having a matrilineal kinship system, exogamous marriage between clans, and organizing into settled villages and towns. Southeastern Woodlands societies were usually divided into clans; the most common from pre-contact Hopewellian times into the present include Bear, Beaver, Bird other than a raptor, Canine (e.g. Wolf), Elk, Feline (e.g. Panther), Fox, Raccoon, and Raptor. They observe strict incest taboos, including taboos against marriage within a clan. In the past, they frequently allowed polygamy to chiefs and other men who could support multiple wives. They held puberty rites for both boys and girls. Southeastern peoples also traditionally shared similar religious beliefs, based on animism. They used fish poison, and practiced purification ceremonies among their religious rituals, as well as the Green Corn Ceremony. Medicine people are important spiritual healers. Many southeastern peoples engaged in mound building to create sacred or acknowledged ritual sites. Many of the religious beliefs of the Southeastern Ceremonial Complex or the Southern Cult, were also shared by the Northeastern Woodlands tribes, probably spread through the dominance of the Mississippian culture in the 10th century. The main agricultural crops of the region were the Three Sisters : winter squash, maize (corn), and climbing beans (usually tepary beans or common beans). Originating in Mesoamerica, these three crops were carried northward over centuries to many parts of North America. The three crops were normally planted together using a technique known as companion planting on flat-topped mounds of soil. The three crops were planted in this way as each benefits from the proximity of the others. The tall maize plants provide a structure for the beans to climb, while the beans provide nitrogen to the soil that benefits the other plants. Meanwhile, the squash spreads along the ground, blocking the sunlight to prevent weeds from growing and retaining moisture in the soil. See