In 1855, due to change in river course part or Serajganj thana was transferred from Mymensingh to Pabna and in 1866, the whole of it was transferred to Pabna. In 1866, thana Dewangajn was transferred to Mymensingh from Bogra and thana Atia from Dhaka. In 1867 for the administrative convenience boundaries of five subdivisions (including Tangail) and Thanas were notified. In 1874 on the basis of survey, the district boundaries were notified. In 1874 the Jamuna (or Daokoba) River was declared the western boundary between Mymensingh and Bogra and as such, 165 villages were transferred to Bogra. In 1875, the Brahmaputra was Made the boundary between Mymensingh and Rangpur and the portion of Patiladaha, east of the river, was transferred to this district form Rangpur. In 1877, the Jamuna was declared the boundary between Pabna and Mymensingh, in the west. On the first of December 1969, Tangail subdivision was separated from Mymensingh and a new District of Tangail was formed. Then in 1977 another new district Jamalpur (including Sherpur) was formed. Mymensingh district was established in 1787, which was later on reorganised into six districts, namely, Tangail, Jamalpur, Kishoreganj, Sherpur, Netrokona, and Mymensingh. Currently, Mymensingh district has a city corporation, eight municipalities and thirteen upazilas. One of the most eminent District Magistrate and Collectors of Mymensingh district was Gurusaday Dutt, Esq., ICS, the first Indian to come first in any part of the Open Competitive Services Examination then held in England. The district covers an area of 4363.48 km2, with several small valleys between high forests. The temperature ranges from 12 to 33 °C, and the annual rainfall averages 2,174 mm. It is at the foot of Garo hills of Meghalaya, and includes some "chars" (sandy islands) founded on the bed of the Old Brahmaputra River and also some ancient forests of mainly a single wood tree, the sal tree. The city of Mymensingh stands on the bank of the Old Brahmaputra, as the 1897 Assam earthquake changed the main flow from Brahmaputra to the Jamuna River which flows west of the greater Mymensingh region.