The county was administratively divided into five districts (plăși):[1] At the end of the Crimean War, by the Treaty of Paris (1856), Southern Bessarabia was returned by the Russian Empire to Moldavia.

Southern Bessarabia was administratively organized into 3 counties: Cahul, Bolgrad and Ismail, and it was part of Moldavia and, after 1859, part of the United Principalities of Moldavia and Wallachia (called Romania after 1866) until 1878, when by the Treaty of Berlin (1878) all three counties were ceded back to the Russian Empire in exchange for Northern Dobruja.

The area returned to Romanian administration as the Bessarabia Governorate following the Axis invasion of the Soviet Union in July 1941.

A military administration was established and the region's Jewish population was either executed on the spot or deported to Transnistria, where further numbers were killed.

According to the census data of 1930, the county's population was 196,693, of which 51.2% were ethnic Romanians, 17.9% Gagauz, 14.5% Bulgarians, 7.5% Russians, 4.4% Germans, 2.3% Jews, as well as other minorities.