Though Bronze Age weapons have been found in Hallau, the first traces of a settlement date from the Roman era.

[3] About two-thirds of the land in Hallau was originally owned by the Benedictine monastery of All Saints in Schaffhausen.

In the 2nd half of the 15th Century the Bishop and the Landgrave of Sulz fought over the High justice rights in the Klettgau valley.

During the Late Middle Ages and the Early modern period the villages expanded.

They purchased the Lauferberg at some point, in 1457 they bought the Vogtei Wunderklingen an der Wutach and in 1507 the weir and water mill.

Of the rest of the land, 8.7% is settled (buildings or roads) and the remainder (0.5%) is non-productive (rivers or lakes).

[6] The precipitation rates are somewhat lower when compared to other places in northern Switzerland due to the Klettgau region's location in the rain shadow of the Black Forest mountains.

Due to the number of old Alemanni graves and artifacts, the church was pilgrimage site until the Protestant Reformation.

[3] Additionally, the entire village of Gächlingen is designated as part of the Inventory of Swiss Heritage Sites.

[10] The blazon of the municipal coat of arms is Gules a Fleur de lis Argent between two Mullets Or in pale.

[8] Border crossings into Germany are located between Hallau town and Eberfingen; and between the village of Wunderklingen with Eggingen, both in Waldshut district in Baden-Württemberg state.