The Magna Carta was signed in order to establish certain rights and limitations on the power of the monarch. It aimed to protect the rights and liberties of the English barons and limit the authority of King John of England. The document addressed issues such as due process of law, protection against unlawful imprisonment, and the right to a fair trial. The signing of the Magna Carta in 1215 marked an important milestone in the development of constitutional law and the concept of individual rights.