Scattered neolithic items indicated that the area around Reinach has been occupied since at least that time. Several Hallstatt era tumuli (at Sonnenberg), Roman era buildings (at Chilebreiti) and Alamanni graves (at Herrenweg) confirm the early settlement of the region. Reinach is first mentioned in 1036 as "Rinacha". At around the same time, the Lords of Reinach (named after their castle of Unter-Rinach, in a neighboring village), owned much of the property in the village. Reinach, together with Menziken, Burg and Wilhof, formed the lands of the Lords of Reinach. The sovereign rights of the Lords of Reinach fell in 1402 or 1404 to the Ribi family, the schultheiss of Lenzburg, and the Alsatian noble family of Mörsberg. In 1572 Reinach separated from Menziken to each become independent municipalities. After the conquest of Aargau by Bern in 1415, Reinach remained the center of the court of Reinach within the bailiwick of Lenzburg.