The direction words — “north,” “south,” “east,” and “west” — are capped when they refer to a recognized region and not capped when they simply indicate a direction.
In CA, for example, we have “Northern CA” and “Southern CA” as recognized regions; we have no region that is recognized as “eastern CA.”
…He lives in Northern California.
…He lives in eastern California.
…I am traveling to the Northwest.
…I am traveling north from Los Angeles.