One from Castile and one from Aragon This treaty was signed at Tordesillas , hence the name of it . The treaty was ratified by Spain ( at the time , the Crowns of Castile and Aragon ) , and by Portugal , . The other side of the world would be divided a few decades later by the Treaty of Zaragoza or Saragossa , signed on , which specified the antimeridian to the line of demarcation specified in the Treaty of Tordesillas .