When the Voortrekkers moved away from the Cape Colony in the Great Trek, some of them settled just north of the Orange River, which formed the border between the Cape Colony and the rest of South Africa. There, they founded many towns and farms. But they soon came into conflict with some of the Black groups, especially the Basotho. The Basotho were a Black nation that was formed by Moshoeshoe after the mfecane. Their capital was at Thaba Bosiu, which means Mountain of the Night in Sotho. In 1853 the Boers (as the Voortrekkers who had settled in the new republics were now called) declared the area the Orange Free State, a Boer republic like the ZAR. They fought against Moshoeshoe many times, mostly over who owned what land and where the border between the OFS and the Basotho-kingdom actually was. During the protracted Second Basotho War of 1864 to 1868, Moshoeshoe asked for British protection to protect his Kingdom. The Basotho kingdom became a British protectorate and the Second Basotho War came to an end. As a measure to appease the Boers, the British granted most of the Basotho’s fertile lands to the Orange Free State creating the current Lesotho borders with the Free State.
When the Second Anglo-Boer War broke out in 1899, the Orange Free State helped the ZAR to fight against the British. But in 1902 the Boers lost the war and their republics became British colonies. The name of the Orange Free State was changed to the Orange River Colony. In 1910, it became one of the provinces of the new Union of South Africa, and the name was changed back to the Orange Free State. After South Africa’s transition to democracy the Orange Free State became a South African province and the name was changed to Free State.
– See more at: http://www.sahistory.org.za/places/free-state#sthash.jTqFGw32.dpuf