Think of signal flags as the19th Century ship-to-shore tweet! In the days before 2-way radio, it was an easy and safe way to get messages between boats at anchor to people on shore. Boats also used flags to relay messages to each other at sea. And remember, at one point in our history, boats were by far the fastest and best way to get around, so there was a lot more traffic then compared to now.

Not only could sailors spell a message, but each signal flag alone also has a separate, complete meaning. For example, when the WHISKEY flag is hauled up the yard arm it means "I require medical assistance." The Hotel flag means "I have a pilot on board."

As short wave radio began to replace flags, sailors used the flags to “dress” their boats for formal occasions and holidays (see vintage postcard above of Newport harbor c. 1905.) Today signal flags are still used for yacht racing and other boating events.

The Peabody-Essex Museum in Salem, Mass is the oldest maritime museum in the USA and the authority on maritime history. Check out their history of signal flags here.