The History of Korea before 1600 is obscure. According to Dalton, Balands were the original rulers of Korea. Baland Kings had their Capital in Sidhi(Their descendants continue to live at Madwas in Sidhi District). There still exist the ruins of many great works traditionally ascribed to them. The temple of Goddess Mahamaya at Kudergarh in Bhaiyathan Block of Surguja District (Parent District of Korea) was built by them. Hills North of Mendra village Near Sonhat are known as Baland Pahar. According to Dalton, a combined force of the Kol Raja and Gonnd Zamindars drove away the Baland rulers from Korea. The Kols were known as Konch Kols and are said to have ruled for Eleven Generations. One view was that they had their Capital at Koreagarh. There is a plateau on the top of Koreagarh and one can see some ruins there. There is a Bauli (Stepped Well) near the ruins. The other view is that the Kol Raja had his capital in village Bachra near Podi and that time Raja was constructing his Capital at Koreagarh. There is an Earthen mound at Bachra village and the villagers say that this was place where the Kol Raja had his residence. It is also po. It is also possible that the Southern portion of Korea was ruled by the Kol Raja and the Northern portion by the Balanda.

In Early 17th century, two cousins of the Agnikul Chauhan Raja of Mainpuri, Dalthmban Sahi and Dharamal Sahi were returing after pilgrimage to Jagannath Puri. They had a small force with them. The route from Mainpuri was via Varanasi, Mirzapur, Sidhi, Surguja, Chotanagpur and Sambalpur. On their return journey, they halted at Bishrampur, the Capital of Surguja State. It has since been named Ambikapur. They camped near the Joda talab which still exists to this day. It was so happened that the Maharaja of Surguja was away from the Capital and some rebel sardars of the State surrounded the palace. The Rani came to know that the Chauhan brothers were camping near the Joda Talab. She sent the traditional Rakhi. Dalthamban Sahi and Dharamal Sahi came to her rescue and drove away the bagi sardars. A major part of their force was killed in the encounter. After some time the Maharaja returned. He thanked the Chauhan ed the Chauhan brothers for rescuing the Rani and offered them the Jagirdari of the area on the Eastern part of the State known as Jhilmili. This was accepted by the older brother Dalthamban Sahi.   A part of Jhilmili Area was under control of Baland Rajas.

The Chauhan brothers settled at Kaskela village on the banks of the River Rehar. They drove away the forces of Baland from the Area and over powered the Pakharias who were perpetually rebelling against the Surguja State. They paid an Annual Tribute to the Surguja State. The title of Bhaiya was conferred on the family by Maharaja Amar Singh. Since after the tying of the Rakhi, the brothers had become bhaiyas of Rani, the ilaka(area) was known as Bhaiyasthan. This was later known as Bhaiyathan. (one of the block of Surguja District). For some time the younger brother Dharamal Sahi stayed with his brother at Kaskela and then became restless, and decided to carve his own kingdom. He gathered a force and moved westward beyond the boundary of Surguja State into Korea State, which was ruled by a Kol Raja. He camped at the village known as Chirmi in the vicinity of Koreagarh. He attacked the Kol Raja and defeated him in the battle and took over the Kingdom of Korea. He stayed at Chirmi for some time and then moved to Nagar village, which village, which he made his capital. As stated earlier, the Northen part of the State was under the Balands of Sidhi. Dharamal Sahi or his descendants drove away Balands from the Northen territory of Korea State. Dharamal Sahi had three sons Deoraj Sahi, Adhorai Deo and Raghorai Deo. On the death of Dharamal Sahi, according to tradition his eldest son Deoraj Sahi ascended the Gaddi. He was issueless and was succeeded by his younger brother’s son Raja Narsingh Deo. He was succeeded by his son Raja Jeet Rai Deo. He was followed by his son Raja Sagar Sahi Deo. On his death, his son Raja Afhar Sahi Deo ascended the gaddi. His son Raja Jahan Sahi Deo succeeded him. He was succeeded by his son Raja Sawal Sahi Deo. On his death his son Raja Gajraj Singh Deo became the King. He was issueless and was succeeded by his nephew Raja Garib Singh son of Lal Dilip Singh Deo. Raja Garib Singh’s younger brother Lal Man Singh was given a Jagir, which was named Changbhakar. He became the Jagirdar of Changbhakar, which had its capital at Bharatpr. Raja Garib Singh was born in 1745 at Nagar. Near about 1765 the forces of Bhosle’s of Nagpur attacked Nagar and forced Raja Garib Singh to pay Chauth. He paid the Chauth for some time and then stopped paying the same to the Marathas. He moved his Capital to Rajauli and then to Sonhat. The capital was moved to the interior for fear of Maratha attacks.

In 1797 the Marathas under Subedar Gulab Khan attacked Sonhat and forced Raja Garib Singh to pay Chauth. Gulab Khan was the Maratha Subedar posted at Ratanpur (Bilaspur district). He came with 200 foot soldiers with matchlocks and 30 cavalary. He was also assisted by the Maharaja of Surguja who sent 80 cavalary and foot soldiers. They ravaged the countryside. On their return journey at Latma Village, the forces of Patna Zamindar attacked them. The Marathas beat a hasty retreat into Surguja State. The Patna Zamindars still have ten swards and war drums captured in the encounter. After the defeat of Modeji Bhosle of Nagpur by the East India Company, the Chhattisgarh States came under the suzerainty of the East India Company. In the Kabuliat executed on 24th December 1819 by Garib Singh, it was agreed that Korea State will pay an annual tribute of Rs. 400/- Changbhakar was treated as a feudal dependency of Korea and would pay a tribute of Rs.386/- to the East India Company. The tribute was to be paid through Korea State. Raja Garib Singh was succeeded by Raja Amol Singh (bAmol Singh (born 1785) on June 1828. He signed an agreement with the East India Company in 1848, the amount of tribute remained the same. After 1848 Changbhakar paid this tribute directly. Raja Amol Singh was a weak Raja, the State was virtually ruled by his wife Rani Kadam Kunwar. After the death of Amol Singh(1864) his son Raja Pran Singh (Born 1857) become the Raja.

 Raja Pran Singh Deo was issueless. After his death (1897) Raja Sheomangal Singh Deo (Born 1874, descendent of Lal Raghorai Deo, third son of Raja Dharamal Sahi) become Raja on 1899. Raja Sheomangal Singh Deo shifted his capital from Sonhat to Baikunthpur in the year 1900. Baikunthpur was more centrally located and thus the state could be better administered from Baikunthpur. He constructed the two tanks and a temple, which are near the new palace. After his death (18th November 1909), his eldest son Raja Ramanuj Pratap Sing Deo (Born 1901) become Raja on 18th Nov 1909. As he was minor, the State was put under court of wards with Gore Lal Pathak Superintendent of Korea State. He continued till 1916. Pandit Gangadin Shukla took over from him and continued till 1918. He was followed by RaghubirPrasad Verma. And finally In January 1925, Raja Ramanuj Pratap Singh Deo was invested with full ruling with full ruling powers and continued till the merge the Korea State in to independent India. Raja Ramanuj Pratap Singh Deo was a strict Administrator and his administration was free from corruption. He represented the ruling Chief, in the second Round Table Conference held in London in 1931. He was exceptionally honest and straightforward. He always considered himself to be the custodian of the State and ruled it with sincerity and efficiency. The income of the Korea State rose from 2.25 lakhs when he ascended the Gaddi in 1925 to 44 lakhs in 1947-1948, and there was a reserve of over rupees one crore when the State was merged with Central Provinces and Berar. In this duration so many works were done. In 1928, construction of Bijuri – Chirimiri Railway Line started and completed on 1931. In 1928 Chirimiri Colliery opened by Bansi lal Abirchand. In 1928 Khurasia collery is started. In 1929, Jhagarakhand Colliery is opened. In 1930 railway communication to Manendragarh is started. In 1935 Ramanuj High School opened. On 15th December 1947, Raja Ramanuj Pratarp Singh Deo signed the merger agreement by which State was merged to the Central Provinces and Berar and finally 1st January 1948, State is merged with Central Provinces and Berar.