A watchman is someone whose job is to guard or protect a place, especially during the night. Before modern security systems and police forces, watchmen would patrol streets and buildings, keeping an eye out for fires, thieves, or trouble. They carried lanterns to light their way and often called out the time and weather conditions: “Twelve o'clock and all's well!”

In colonial America and medieval Europe, watchmen were essential guardians of their communities. They might sound an alarm by ringing a bell or blowing a horn if they spotted danger. The phrase “the city never sleeps” partly comes from the tradition of watchmen staying alert through the dark hours while everyone else rested.

Today, we might call a watchman a security guard or night watchman. You might encounter a watchman at a museum, warehouse, or construction site. The word can also be used more broadly for anyone who carefully monitors something: a person who tracks political changes might be called a watchman for democracy, staying alert to threats against freedom.

The related word watchdog works similarly, describing either an actual guard dog or someone who monitors an organization to prevent wrongdoing.