Louis XXIV
Le Roi Soleil
I personally agree with the majority opinion here that north-south divides aren't all that important for empires. I think it's an obstacle to overcome, of course (anything that divides your empire geographically is one more obstacle to face), but not an insurmountable one.
That being said, there is something to be said for the north-south axis when it comes to agriculture. Some crops grow in one climate but can't grow in another. Sorghum, for example, grows in the Sahel Zone, but did not grow south of there. This was a problem for the spread of agriculture and the Bantu migration. By the time the Bantu peoples made it to southern Africa, they no longer had Sorghum or any of the other crops that grew up there. Likewise, the spread of Mesoamerican corn into the northeast United States was slowed by the need to develop a corn that could deal with the cooler temperatures. The north-south divide for agriculture was a bit more significant than an east-west divide.
That being said, there is something to be said for the north-south axis when it comes to agriculture. Some crops grow in one climate but can't grow in another. Sorghum, for example, grows in the Sahel Zone, but did not grow south of there. This was a problem for the spread of agriculture and the Bantu migration. By the time the Bantu peoples made it to southern Africa, they no longer had Sorghum or any of the other crops that grew up there. Likewise, the spread of Mesoamerican corn into the northeast United States was slowed by the need to develop a corn that could deal with the cooler temperatures. The north-south divide for agriculture was a bit more significant than an east-west divide.