Originally, Bladen was a vast territory with indefinite northern and western boundaries. Reductions in its extent began in 1750, when its western part became Anson County. In 1752 the northern part of Bladen County was combined with parts of Granville County and Johnston County to form Orange County. In 1754 the northern part of what was left of Bladen County became Cumberland County. In 1764 the southern part of what remained of Bladen County was combined with part of New Hanover County to form Brunswick County. In 1787 the western part of the now much smaller county became Robeson County. Finally, in 1808 the southern part of Bladen County was combined with part of Brunswick County to form Columbus County.
By 2005 55.8% of the population of Bladen County was non-Hispanic whites. 36.8% of the population was African-American. 5.0% of the population of was Latino. 2.3% of the population was Native American.
There were 12,897 households out of which 30.40% had children under the age of 18 living with them, 48.90% were married couples living together, 15.70% had a female householder with no husband present, and 30.70% were non-families. 27.70% of all households were made up of individuals and 11.50% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 2.97.
In the county the population was spread out with 24.60% under the age of 18, 8.70% from 18 to 24, 27.20% from 25 to 44, 25.20% from 45 to 64, and 14.20% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 92.60 males. For every 100 females age 18 and over, there were 88.70 males.
The median income for a household in the county was $26,877, and the median income for a family was $33,974. Males had a median income of $27,799 versus $21,973 for females. The per capita income for the county was $14,735. About 16.60% of families and 21.00% of the population were below the poverty line, including 28.70% of those under age 18 and 24.20% of those age 65 or over.