King Sejong and Hangeul
Hangeul (한글), otherwise known as the Korean alphabet, was created by the forth king of Joseon — Sejong the Great. It was established in the 15th century. The basic Korean alphabets consist of 14 consonants and 6 vowels. Hangul was promulgated by Sejong the Great, the fourth king of the Joseon Dynasty. The Hall of Worthies is often credited for the work.
The project was completed in late December 1443 or January 1444, and described in 1446 in a document titled Hunmin Jeongeum (“The Proper Sounds for the Education of the People”), after which the alphabet itself was named. The publication date of the Hunmin Jeong-eum, October 9, became Hangul Day in South Korea. Its North Korean equivalent, Chosongul Day, is on January 15.
Various speculations about the creation process were put to rest by the discovery in 1940 of the 1446 Hunmin Jeong-eum Haerye (“Hunmin Jeong-eum Explanation and Examples”). This document explains the design of the consonant letters according to articulatory phonetics and the vowel letters according to the principles of yin and yang and vowel harmony.
In explaining the need for the new script, King Sejong explained that the Korean language was fundamentally different from Chinese; using Chinese characters (known as hanja) to write was so difficult for the common people that only privileged aristocrats (yangban, 양반), usually male, could read and write fluently. The majority of Koreans were effectively illiterate before the invention of Hangul.
Hangul was designed so that even a commoner could learn to read and write; the Haerye says “A wise man can acquaint himself with them before the morning is over; a stupid man can learn them in the space of ten days.”