The world map shows the boundary line between the spheres of influence of the world’s first great powers in 15th century, Spain and Portugal. The vertical line from pole to pole was a line that drawn by naval force and religious force. The Treaty of Tordesillas in the 15th century indicated that the national language of the eastern part of South America, which is Portuguese, differs from the national language of the western part of South America, which is Spain, in the 21st century.