[3] The Strait of Magellan was discovered by the Spanish in 1520, providing a sea route between the Atlantic and the Pacific that ran between South America and the archipelago of Tierra del Fuego.

[4] The strait averages just over 4 miles (6.4 km) wide, and is much narrower in places, forming a "V" shape pointing south.

[5] Early in the seventeenth century it became known that the Dutch navigators Jacob Le Maire and Willem Schouten had found a new and safer route farther south.

Philip III of Spain arranged for an expedition of two ships to verify the discovery, which left Lisbon in September 1618.

He was appointed the main pilot in the 1618 expedition led by the brothers Bartolomé and Gonzalo García del Nodal to explore the Straits of Magellan.

Ramírez was charged with astronomical observations and with preparing charts with the help of Juan Manso and seven other pilots, four in each caravel.

The two caravels navigated without difficulty to the southern extreme of the American continent, resting on the way for a few days at Rio de Janeiro.

Ramírez, assisted by the pilot Juan Manso, collected the material needed to draw the first comprehensive sea chart of the southern part of Patagonia.

The circumnavigation showed that Tierra del Fuego was an island, not a northern extension of the "Terra Australis" southern continent as had been thought.

Diego Ramírez de Arellano was made honorary captain of the Spanish infantry, and was given the title of almirante.

[1] Captain James Burney called the discovery of the Diego Ramírez Islands the most remarkable event of the voyage, since for a century and a half they were the most southerly points marked on any chart.