[1] Its county seat and largest city is Cooper.

[2] The county was founded in 1870 and is named for its triangular shape,[3] which resembles the Greek letter delta.

Meanders of two forks of the Sulphur River formed its northern and southern boundaries and meet at its easternmost point.

[5] The 2020 U.S. census determined that Delta County had a population of 5,320.

[8] Among its population, the racial and ethnic makeup was 80.10% non-Hispanic white, 5.97% African American, 0.80% Native American, 0.71% Asian, 0.10% Pacific Islander, 0.57% some other race, 4.23% multiracial, and 7.53% Hispanic or Latino of any race.