Final answer:
The Peace of Augsburg was signed in 1555, establishing the legality of Lutheranism alongside Catholicism within the Holy Roman Empire.
Step-by-step explanation:
The Peace of Augsburg was signed in the year 1555 during the reign of Charles V, the Holy Roman Emperor. This important treaty recognized the legality of Lutheranism alongside Catholicism within the Holy Roman Empire and allowed each ruler to choose the religion of their own territory, a principle known as cuius regio, eius religio. This was a significant step towards religious peace in the territories of the empire, although it only accommodated Lutherans and did not extend tolerance to other religious groups such as Calvinists or Anabaptists.