Using the U.S. Census definition of poverty, an attempt was made to determine: how many poverty level South Dakota families there were in 1970 and where they resided; the socioeconomic factors explaining county differences in poverty incomes; whether those factors explaining poverty incidence would correlate with county differences in the extent of migration between 1960 and 1970. Classifying residents as rural farm, rural nonfarm, and urban, a determination was made of poverty level families in each county (number and percentage). Characteristics (62 variables) measuring county population by age and sex, numbers of males and females employed by occupational categories, income, and educational and marital status for the 3 sectors were examined, and then 10 of these variables were examined in terms of migration. Results indicated: the incidence of disadvantagement was greatest in rural farm and rural nonfarm areas; family disadvantagement for the county as a whole prevailed in most of South Dakota; 1970 family disadvantagement was primarily a consequence of families with a female head and concentrations in the male labor force of farm managers and operatives; high outmigration between 1960 to 1970 was due to a high proportion of families with female heads and low employment for rural farm males either in high income employment sectors or as farm managers and operators. (JC)