The important document signed in 1215 is the Magna Carta, also known as the Great Charter. It was sealed by King John of England in Runnymede, near London, as a result of political conflict with his barons. The Magna Carta established the principle that everyone, including the king, was subject to the law. It contained provisions for protecting the rights of the nobility and addressing grievances over taxation and justice. Over time, it has come to symbolize the foundation of modern democracy and constitutional law, influencing various legal systems and documents, including the United States Constitution.