Very little is known about the early history of what is now Nagaland, including the origin of several large sandstone pillars at Dimapur. British rule was established over the area by the 1890s, and headhunting, then a traditional practice, was outlawed. The Naga territory remained split between Assam and the North East Frontier Agency after Indian independence in 1947, despite a vocal movement advocating the political union of all the Naga tribes; one faction called for secession from India. In 1957, following violent incidents, the Indian government established a single Naga administrative unit under Indian rule. The Naga people responded by refusing to pay their taxes and by conducting a campaign of sabotage. In 1960 the Indian government agreed to make Nagaland a self-governing state within India; the state was officially inaugurated in 1963.