Data come from the decennial U.S. census for the time period 1950 to 1990. Also included are 1998 census estimates of population released in March of 1999. Analysis of rural and urban characteristics of the population is confined to the decennial census data since the estimated 1998 population data does not make this distinction. Because of this, some of the data compiled in the tables and texts are for the time period 1950 to 1990 and some are for the time period 1950 to 1998. Despite the 1990 data being somewhat out of date, the reported trends are still worthy of consideration with implications for the 1990s.