Komárom-Esztergom County
In 1920 the Treaty of Trianon assigned the part of Komárom county north of the Danube to Czechoslovakia (Komárno region). The southern part stayed in Hungary and merged with the southern part of Esztergom county to form Komárom-Esztergom County in 1923. The forming of Czechoslovakia, whose border in the south became the Danube River, separated the seat of the county, Komárom, from its southern half.