Throughout Iowa's population history, migration of families and persons into, out of and within the state has played an important role in the growth, distribution and concentrations of the state's population.
Prior to 1900 the state gained more than a million persons through net immigration and since 1900 it has lost more than a million through net out-migration or the equivalent of two-fifths of its present population.
The turn of the century marked the entry of Iowa into the list of states with relatively stable population numbers characterized by a comparatively slow growth. About 1900, natural increase superseded in-migration as a source of population growth, and rural to urban migration became increasingly important in redistributing population in relation to employment opportunities and resources within the state.
Jehlik, Paul J. and Wakeley, Ray E.
"Rural-Urban migration in Iowa, 1940-50,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 31
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol31/iss407/1