Unlike many of the other southern tribes, Quapaw society was based on a patrilineal structure. This means that people traced their ancestors through their father and adopted their father's clan.
Based on what we know about other Dhegiha Siouan groups, clans were probably an important part of Quapaw social structure. There were approximately 21 social units, perhaps clans, at one point, each named after an animal (bear, rabbit), stellar object (star), or weather event (thunder). Members of a clan were considered each other's blood relatives. Because of this people were expected to marry outside of their clan. When a woman married, she would not become part of her husband's clan. Instead, she would remain the same clan as her father. Their children would, in turn, be members of their father's clan.
The Quapaw, like other Dhegiha Siouan tribes, grouped clans into two major divisions (or moieties) - the Earth People and the Sky People. In addition to marrying outside a person's clan, people were expected to marry outside of their moiety. Each moiety served a different function. The Earth People generally handled the material administrative details of the tribe's well being, while the Sky People tended the spiritual aspects of tribal life. Because each couple was composed of a Sky Person and an Earth Person, the children of each couple would be exposed to both aspects of tribal life.