The Church of St. Nicholas, probably a Homburger family church, is first mentioned in 1180. Starting in 1407 the patronage rights were transferred from the Habsburgs to the Collegiate church of Rheinfelden. In 1651 the nave and tower were expanded and renovated, while in 1718-19 the choir was completely rebuilt. The Chapel of Saint Verena was built in 1516 on the foundation of the Early and High Middle Ages manor chapel. Verena newly built chapel on foundations from the early and HochMA and belonged to the manor. Even today, Herznach and Ueken form a parish. Until the Protestant Reformation this parish included Densbüren and the village of Asp and until 1852 it included Zeihen. With the Act of Mediation in 1803, the "Fricktal" joined the Canton of Aargau and Herznach and Ueken became independent municipalities. The two former population centers Unterherznach (walled church district) and Oberherznach (mill) grew together along the road by 1811.