1. *Chuseok* is a big holiday in Korea.

2. *Chuseok* is a big holiday of Korea.
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Can we use both sentences? What is the difference between 'in Korea' and 'of Korea'? Does 'in Korea' modify 'a big holiday'? Does 'of Korea' modify 'a big holiday'?

I think it would be in Korea, simply because it's more proper.