Arunachal Pradesh is a state in Northeastern India. It was formed from the erstwhile North-East Frontier Agency region, and became a state on 20 February 1987. It borders the states of Assam and Nagaland to the south. It shares international borders with Bhutan in the west, Myanmar in the east, and a disputed border with China in the north at the McMahon Line. Itanagar is the state capital of Arunachal Pradesh. Arunachal Pradesh is the largest of the Seven Sister States of Northeast India by area. Arunachal Pradesh shares a 1,129 km border with China's Tibet Autonomous Region.