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

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: 37.4% were Reformed (Calivinist), 34.6% were Roman Catholic, 20.6% Unitarian, 3.7% Orthodox Christian, 1.1% Jewish, and 1.1% Greek-Catholic, as well as other minorities.

[3] In 1930 the urban population of Odorhei County was 8,518, which included 81.3% Hungarians, 11.3% Romanians, 3.3% Jews, 2.0% Germans, and 1.4% Roma by ethnicity, as well as other minorities.

The religious mix of the urban population was 51.3% Roman Catholic, 25.9% Reformed, 8.0% Eastern Orthodox, 5.3% Unitarian, 3.7% Jewish, 3.3% Greek-Catholic, and 1.9% Lutheran, as well as other minorities.