It's proving quite difficult to learn some of the facts about written Korean before hangul was given official status by the government.
We know that metal movable type printing was inventing in Korea in the 13th century.
We know that hangul was devised in the 15th century.
We know that various forms of popular literature flourished from the 16th and 17th centuries.
We know that hangul was adopted in official documents for the first time in 1894.
Yes literacy was not widespread until quite recently, but it seems apparent that plenty of documents were written and printed, at least by the government, prior to 1894, without hangul.
So which system was the most used, or the official system used by the government before 1894?