In the 11th and 12th centuries the the Counts of Lenzburg ruled the Aargau, including the area of Beromunster and Reinach. When that family died out in 1173, the Counts of Kyburg inherited their possessions, to be succeeded after 1264 by their heirs the Counts of Habsburg.
In 1273 Rudolf, Count of Habsburg was elected Emperor of Germany. The family afterwards became Archdukes of Austria. They moved their capital from Habsburg, a castle in the Aargau, to the city of Vienna in Austria. The Habsburg subjects in what is now central Switzerland rebelled and formed the Swiss Confederation. In 1415 the Swiss Confederates conquered the Aargau from the Habsburgs and annexed it to Canton Bern. It remained a part of Bern until 1798 when the French conquered Switzerland and made the Aargau a separate canton.
The Herren von Reinach (Rinach) family were ministerialen, or servants, of the Counts of Habsburg. They ruled the upper Wynental as Habsburg deputies until the Bernese conquest in 1415. They claimed to be a branch of the von Habsburgs, and bore a similar coat of arms, but their claim was largely discredited in the mid-20th century. The Stammvater of the family was Arnold von Reinach (fl. 1210), who built the family seat at Burg unter Reinach in the 12th century. Ulrich I and Kuno von Rinach, the sons of Hesso von Rinach, also built the castle of Obere Reinach at Herlisburg in the 13th century. If Arnold von Rinach was the person who was said to have been son of a Count von Habsburg, the likeliest candidate seems to have been Albrecht III von Habsburg.
The family’s castles of Burg unter Reinach and Obere Reinach were destroyed in 1386 during the Sempach War and not re-built. The von Reinach family remained in Habsburg service and entered the Austrian nobility. Today they are represented by the Baron de Reinach, who lives in Alsace. The ruins of Obere Reinach are still owned by the Barons of Reinach.
The first mention of the village of Reinach was in 1036, but it seems to have been a Roman settlement (as are all places in Switzerland with the ending –ach, from the Latin –acum). The low jurisdiction was in the possession of the Herren von Rinach. The tithe went to the church at Beromünster. Hesso von Rinach (died about 1280) was a Canon of Beromunster and Prior of Schönenwerd. Jacob von Reinach (died 1368) was also a Canon of Beromunster. After the Swiss Confederates conquered the Aargau in 1415, Reinach became subject to Berne. Pfeffikon was detached from Reinach in 1528, and Menziken in 1580.