Square-rigged describes a sailing ship whose main sails hang from horizontal poles (called yards) that cross the mast at right angles, forming a square or rectangular shape. Picture a classic pirate ship or the tall ships you see in old paintings: those massive rectangular sails stretched across horizontal beams are square sails.

Square-rigged ships were the workhorses of ocean exploration and trade for centuries. Ships like the Mayflower, which carried the Pilgrims to America, and the great naval vessels that fought in battles like Trafalgar were square-rigged. These ships could carry enormous amounts of sail, making them powerful in open-ocean sailing, especially when the wind blew from behind.

However, square-rigged ships had limitations. They couldn't sail as close to the wind as modern fore-and-aft rigged boats (which have triangular sails running along the length of the ship). This meant square-rigged captains needed expert knowledge of winds and currents to navigate effectively. Despite requiring large crews to handle all those sails, square-rigged vessels dominated long-distance sailing until steamships replaced them in the mid-1800s.

Today, square-rigged ships survive mainly as training vessels and floating museums, though they remain magnificent examples of human ingenuity and maritime heritage.