Mangan serves as the headquarters of:

West Sikkim District
East Sikkim District
North Sikkim District
South Sikkim District

Mangan serves as the headquarters of West Sikkim District. It is a town in the Indian state of Sikkim. It is the headquarters of West Sikkim district and is located in the foothills of the Himalayas. The town is known for its scenic beauty and its many temples and monasteries. Mangan is also a popular tourist destination.

The other options are incorrect because they are not the headquarters of West Sikkim District. East Sikkim District is headquartered in Gangtok, North Sikkim District is headquartered in Namchi, and South Sikkim District is headquartered in Namchi.