The territory was expanded over time by several other kings. The borders of the Bamoun kingdom were drawn by King Mbouombouo, the 11th king of the Bamoun dynasty. He surrounded the entire Bamoun kingdom with walls. This administrative structure created by King Mbouombouo remained in force until the beginning of the 1900s during the reign of King Njoya, the 17th King of the Nchare Yen dynasty.

The first campaign of topographic mapping took place between April and October 1912. King Njoya accompanied the travels of a team of about twenty people, among whom were a number of collaborators who had taken an active part in the invention of writing: Nji Mama Pekekue who coordinated the whole thing, his brother Ibrahim Njoya who invented a tradition of Bamoun drawings.

Since 1981, the Bamoun kingdom has been called the NOUN DEPARTMENT, the name of the river that irrigates its lands. It is made up of 17 groups and 166 villages covering an area of 7,687 km2. The department shares its borders with five other departments of the Republic of Cameroon which are: Mayo Banyo and Donga Mantoung in the North; Mbui and Ngoketunja, Bamboutos, Mifi and Khoug-khi in the West; Mbam and Nkim and Ndé in the East and South.

The land surveying allowed the different Kings to discover the richness of the kingdom. The soil was fertile and made the local population directly very active in the agricultural field. The kingdom was organized in such a way that each family had the right to exploit the land. There is the farming of food products, coffee, palm trees, safous, peanuts, beans, corn and many others. Thanks to the hard work of the population, the NOUN department (Bamoun kingdom) is considered as the breadbasket of Cameroon. Agriculture accounts for 60% to 70% of the active population and contributes to more than 60% of its wealth.