After annexation of the Brahmaputra Valley in 1826, British colonialism gradually subjugated the contiguous hills and plains and brought them under the colonial province of Assam. The territory of the colonial province was substantially expanded to include the Cachar Plains in 1830, Khasi Hills in 1833, Jaintia Plains in 1835, areas under present Karbi Anglong and North Cachar in 1838 and 1854 respectively, Naga Hills during 1866-1904, Garo Hills in 1872-73 and Lushai Hills in 1890.