The Treaty of Tordesillas

The Monastery of Santa Clara in the old Castilian market town of Tordesillas was originally built as a royal palace. Today, its Gothic church and Mudejar courtyards make it a tourist attraction where the romantics among them imagine the haunting presence of Juana, the mad Queen of Spain, who spend endless years there cowering on the floor of a dark room, while her son, the emperor Charles V, ruled and ruined the world’s largest empire.

In 1494, during the reigns of Ferdinand and Isabella, the palace was the site of an important treaty, in which Portugal and Spain entered into a boundary agreement to modify the "Pope’s line". A year earlier in May 1493, Pope Alexander VI, the Spanish Borgia whom his critics like to remember mostly for his enormous wealth, his mistresses, and his ten illegitimate children, had been pressured by king Ferdinand to draw a line across the Atlantic and define spheres of influence.

Portuguese sailors had rounded the Cape of Good Hope, that promised an eastern route by sea to India, and Columbus had just returned from his historic voyage stirring old rivalries between the two seafaring nations. Both countries were anxious to legitimize past, present, and future claims of discovery, the magnitude of which could as yet only be imagined. In his bull Inter caetera, and at the suggestion of Columbus, the Pope drew the line of demarcation one hundred leagues west of the Azores, granting Portugal most of the South Atlantic and allowing Spain to claim whatever it would discover west of that line.

A year later, miffed by the pope’s revocation of earlier concessions, the Portuguese were having second thoughts. Like an unhappy landowner whos fancied location of his boundary is rudely corrected by the superior knowledge of a surveyor, they clamored to have the deal renegotiated and threatened war. Columbus was away on his second voyage and thus could not be consulted, but pressed by circumstances Ferdinand and Isabella agreed to a modification of the line.

The ambassadors of Spain and Portugal met in Tordesillas, and there on the seventh day of June, 1494 they put their names to a treaty in which they agreed to a line of which neither party knew whether or not it touched land. It was resolved that: "…a boundary or straight line shall be determined and drawn north and south…from the Arctic to the Antarctic pole. This boundary or line shall be drawn straight, as aforesaid, at a distance of three hundred and seventy leagues west of the Cape Verde Islands, being calculated by degrees [emphasis added]… And all lands, both islands and mainlands, found…by the said King of Portugal…on the eastern side of the said bound, shall belong to…the said King of Portugal and his successors." Everything west of the line was deeded to Ferdinand and Isabella. How far east or west nobody said, so that soon after, when the Portuguese had crossed the Pacific and discovered the Moluccas, they wondered: where does east meet west?

Accurately locating the line of Tordesillas on the face of the earth would be a lawyers dream and a surveyors nightmare. Early cartographers placed it anywhere between 46 and 49 degrees west of Greenwich, reserving for Spain the mouth of the Amazon that is at 50 degrees. In order to place the line this far west one must assume a diminished size of the globe. My own interpretation is as follows:

In 1494 the length of a degree of the earth circumference was not known, but was assumed by Columbus to measure the equivalent of 56.66 statute miles, which is only 82% of the true value of a degree at the equator and only 85% of its length in the latitude of Cape Verde (15 degrees). The westernmost of the Cape Verde islands is roughly in longitude 25 degrees west. Using Columbus’ degree and reducing it to latitude 15 degrees, 370 common leagues (legua comun) of 6666.67 varas translate into about 23 degrees 27 minutes, placing the treaty line approximately at 48 1/2 degrees west. Other locations based on different assumptions are possible.

Brazil was not discovered until 1500 when the fleet of the Portuguese navigator Pedro Alvares Cabral was blown by storms onto an unknown coast, where Cabral (he should properly be called Alvares) promptly used the treaty line of Tordesillas to claim the place for Portugal. Two years later his king sent the Florentine explorer Americo Vespucci to investigate what Cabral had found, and in 1507 Americo’s name was used by the German cartographer Martin Waldseemuller to name the continent "America".

Ignoring everything else that might be said about the Treaty of Tordesillas, it clearly is a legal description. Preparing deeds to real estate in ignorance of geography neither started nor did it end with the treaty makers of Tordesillas, but in fairness to them one must allow that the treaty was based on the best information that could be obtained in 1494. No such allowance can be made today to anyone who writes a deed description without the aid and advise of a professional surveyor.

About the Author

Fred Roeder, LS

Fred Roeder lives in Tularosa, New Mexico. He emigrated to the United States from Germany in 1957 and spent most of his surveying career in the Southwest, working for the U.S. Forest Service. Now retired, he started writing a regular column for the New Mexico Professional Surveyors Newsletter in 1988. In 1994, NMPS produced Antepasados, a book of his columns. Many surveyors are good writers, especially about technical or legal matters. However, it's not often that we find a surveyor/story-teller who can present historical facts in a manner that makes them fun to read. Fred Roeder is such a writer and we are pleased to present more than 80 of his stories here. Bibliography is a list of the books Fred used in his writings, and includes a numbered index of the articles. Index is a list of all the articles Fred has written and when. Editor's pick: The King Who Had No Title
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