Where did giving someone the key to the city originate?

The tradition of giving a "key to the city" dates back to ancient times, symbolizing the granting of freedom and trust to an honored guest or resident. In medieval Europe, cities would often close their gates at night for safety, and a key represented access and privilege. The modern practice began in the 19th century, often as a ceremonial gesture to recognize distinguished individuals or achievements. Today, it serves as a symbolic honor rather than a literal key.