(This poster above says "The birth of Hangul" 한글의 탄생)
Brief History
The Korean alphabet, also known as Hangul is the native alphabet of the Korean language. It was created during the Joseon Dynasty in 1443 by King Sejong the Great, the fourth king of the Joseon Dynasty.
The origin of Hangul involved complex linguistic work by its initial inventors. Prior to the invention, Koreans used Chinese characters called hanaja (fundamentally different from Chinese). However, this was very difficult so only the privileged aristocrats were able to read and write fluently. So back then, majority of Koreans were illiterate. Thus, King Seong designed hangul so that even a commoner could learn to read and write. The document describing this project is called Hunmin Jeung-eum. 
(A page from Hunmin Jeong-eum and a statue of King Sejong)
Name
The modern name Hangul means great (han) script (gul).