The territory of Ciuc County was transferred to Romania from Hungary as successor state to Austria-Hungary in 1920 under the Treaty of Trianon.

In 1938, King Carol II promulgated a new Constitution, and subsequently he had the administrative division of the Romanian territory changed.

In 1940, the county was transferred back to Hungary with the rest of Northern Transylvania under the Second Vienna Award.

Beginning in 1944, Romanian forces with Soviet assistance recaptured the ceded territory and reintegrated it into Romania, re-establishing the county.

[2] Classified by religion: 81.3% were Roman Catholic, 13.8% Greek-Catholic, 1.7% Jewish, 1.9% Reformed (Calivinist), and 1.3% Orthodox Christian.