Portuguese map-maker Pedro Reinel drew the first prime meridian (starting point for measuring
longitude) on a sailing chart in 1506.
While the Portuguese
fixed zero longitude at the Madeira Islands for their overseas voyages, their competitors, the Spaniards, soon chose nearby Ferro (Hierro) in their territories (Canary Islands) for their zero longitude. (shown with red-and-yellow flag on map at left.
By the nineteenth century, when the English achieved dominance at sea, they began producing charts using their own island for zero longitude. In 1884 a conference held in Washington, D.C. ratified
the placement of the prime meridian in Greenwich
England.
While the most common prime meridian, to this day, more than a dozen countries do NOT use the Greenwich meridian (for their maps) including Austria, Norway, Switzerland, and Indonesia.