When were South Korea and North Korea established as separate states?

South Korea and North Korea were formally established as separate states in 1948, following the failure of efforts to create a unified government for the peninsula.12

• South Korea: The Republic of Korea was inaugurated on August 15, 1948, following elections held in the south under the observation of the United Nations.12
• North Korea: The Democratic People’s Republic of Korea was proclaimed on September 9, 1948, after elections for the Supreme People’s Assembly were held in the north.12

Each government claimed to be the sole legitimate authority over the entire Korean Peninsula, a conflict that eventually led to the Korean War in 1950.2