北 is a picture of two people standing BACK to back — and that's the key: 北 originally meant 'back / to turn one's back'. Since you turn your back to the cold north, it came to mean the northern direction. (The 'back' meaning then took the new character 背.)
北 is north — and it opens 北京 (Běijīng), 'Northern Capital', China's capital. Its opposite-pair 南北 (south-north) names the country's great divide: the wheat-eating, drier North vs the rice-eating, wetter South. 东北 ('east-north') is the Northeast / Manchuria. To 'flee north' or face north was historically to face the cold and the frontier.
Two people back-to-back — turning your back to the cold NORTH.
北 ('north') hides its old meaning, 'back' — two people back-to-back. 北京 = 'Northern Capital'. The North/South (北/南) line splits China into wheat-eaters and rice-eaters.