Is South a proper noun

No, the noun 'south' is a common noun, a general Word for a point on a compass or a direction.

A common noun is capitalized only when it is the first Word in a sentence.

A proper noun is the name or title of a specific person, place, or thing; for example:

• Sir Arthur South, Lord Mayor of Norwich
• South America
• South Africa
• New South Wales, Australia
• South Beach, FL
• South Street, St. Paul, MN
• "Tales of the South Pacific" by James A. Michener
• "South Park", Animated TV Series

The directions north, east, south, and west are all common nouns.