This story originally appeared in the September 2014 issue of mental_floss magazine. Subscribe to our print edition here, and our iPad edition here.

There’s nothing inherently upward about North. Some early Egyptian maps put South on top, while in medieval Europe, Christian cartographers tended to give that distinction to the East, since you had to turn that way to face Jerusalem. Others placed East on top because of the rising sun (that’s why we orient ourselves). And early American settlers sometimes used maps with West on top, because that was the direction they were often heading.

If anyone deserves the blame for today’s northward bias, it’s Claudius Ptolemy. In the second century, he wrote the influential Geographia, which featured a “global” map with North on top. No one’s positive why he positioned it that way, but it may be that the Library of Alexandria—where he did his research—simply didn’t have much information on the Southern Hemisphere. During the Renaissance, Ptolemy’s work was revived. By then, magnetic north had been discovered, making his layout even more appealing to mapmakers.