South Korea–United States relations
Following Japanese surrender at the end of the Second World War, the Allied Powers divided the Korean peninsula along the 38th Parallel with two occupation zones with the United States in the south, and the Soviet Union in the north that would later become North Korea. On August 15, 1948, the southern half of Korea declared independence as the Republic of Korea with Syngman Rhee as president. The United States recognized the Republic of Korea as an independent state on January 1, 1949 and diplomatic relations between two countries were established on March 25 in the following year.
Cross-border skirmishes and raids at the 38th Parallel escalated into open warfare when the North Korean forces invaded South Korea on June 25, 1950. The Korean War broke out when North Korea invaded South Korea. In response, 16 member countries of the United Nations, including the United States, came to the defense of South Korea. It was the first significant armed conflict of the Cold War with extensive deployment of American and other troops.
Public holidays in South Korea
These days celebrate events considered joyous to Korea. In the beginning, Independence Declaration Day (March 1) was first stipulated in 1946. After the establishment of the Government of the Republic of Korea in 1948, four major National Celebration Days (Independence Declaration Day, Constitution Day, Liberation Day, National Foundation Day) were provided by "The Law Concerning the National Celebration Days" (국경일에관한법률) in 1949. 
In 2005, Hangul Day became the 5th National Celebration day.