The peace treaty accurately described the plebiscite zones, both in words and by reference to a map. Furthermore, guidelines were given as to who was entitled to vote.
Any person over the age of twenty, born in the plebiscite area, or resident there since before 1 January 1900, or who had been expelled from there by the German authorities without retaining his or her residence, was entitled to vote. During the preparation of the Treaty of Versailles, however, an error crept in to the text, making it possible for all who had been born in the area to vote, irregardless of residence. People were to vote in that local authority in which they were resident, or from which they came.
Danish and German organisations dug out information about all those from near or far who were entitled to vote and urged them to take part in the plebiscite. In this way, the event left its mark far beyond the plebiscite area.
Information centres were opened in the larger towns. In Denmark, it was the national associations who took up the task of helping to make things work in practice; in Germany, the home soil associations had this function.
Travel had to be arranged for the voters, in flag-bedecked trains or special ships. When they arrived they were given a warm welcome and were given lodging with relatives, old friends or families of the same political sympathies..
In Zone 1, the plebiscite was held on 10 February 1920. The weather was very bad that day, with stormy winds and rain, but when the ballot stations closed, the outcome was clear.
111,191 people were entitled to vote, of which 27,853 came from outside the area. In all, 101,632 of them had cast their vote, corresponding to 91.4 %. 75,431 (74.9 %) voted for Denmark, while 25,329 (25.1 %) voted for Germany.
There were German majorities in the towns of Aabenraa, Sønderborg and Tønder, as well as in the village and country parish of Højer, and in the parishes of Ubjerg and Tinglev. However, these majorities did not affect the overall result, and when the first returns were announced in the evening there was great rejoicing among the Danish population of North Schleswig.
The plebiscite in Zone 2 on 14 March produced quite a different result. In this zone, 71,104 people were entitled to vote, and 64,524, or 90.75 %, did in fact do so.
Here, too, the result was clear. 51,724 (80.2 %) votes were cast for Germany, and 12,800 (19.8 %) for Denmark. Any doubt about the way people felt in the town of Flensburg was removed: 27,081 (75.2 %) votes for Germany and 8,944 (24.8 %) for Denmark.
The result in Flensburg created a deep, dark feeling of defeat among the Danish-minded population. The German population, on the other hand, gathered for demonstrations and joyous processions. At midnight the church bells rang and thousands of voices joined in the singing of the hymn, ‘Nun danket alle Gott’.