On 26 May, 1876, a treaty was signed by Amir Yaqoob Khan of Afghanistan with the British Government at Gandamak. Thus the conflict which emerged as a result of the first and second Afghan war came to an end.

In 1883, Quetta was formed into a separate single administrative unit (Quetta - Pishin district). Due to its geo-strategic importance, the British built Quetta as a garrison town. They extended the roads and railway network to Afghanistan and Iran. This situation remained unchanged till the partition of the Sub-continent in 1947.

Under the one-unit system from 1955 to 1970, Quetta and Kalat were the administrative units in West Pakistan. After abolishing the unitary system, Quetta was declared as Capital of Balochistan. Till 1975, Quetta and Pishin were a single administrative unit. In that year Pishin was declared a separate district.

Very little is known about the human settlement in the district. However, it is certain that the Afghans and Brahuis are recent immigrants. The Pashtoons appear to have entered the district from the north east, emigrating from their home round the Takht-i-Sulaman. Kasis (A branch of Afghan) are said to have migrated from their home around the Takht-i-Sulaman about eight centuries ago. They made their first settlement at Samli, a village near Quetta city. The Brahuis are an offshoot from the Kalat territory and their presence in the district dates back to the eighteenth century.

With the passage of time, Quetta began to expand and soon it turned into a beautiful small town. The British paid special attention to its cleanliness. However, 31 May, 1935 was a black day in the history of Quetta. An earthquake destroyed Quetta city completely. The Cantonment area survived to a great extent.

The reconstruction started soon after. Till 1947 Quetta was a small town. People used to call it small London. But rapid population growth in terms of rural - urban migration, and influx of Indian refugees increased the population at Quetta. Influx of Afghan refugees during the 1980s helped the slums to grow. New settlement in the form of housing schemes emerged at Satellite Town, Jinnah Town, Samungli Town, Model Town and Shahbaz Town. In Kachi Abadies, slums also begun to develop. The process of settlement continues. Now Quetta has turned into an over-populated city.

There are some mounds and karezes of ancient time in the district. The most important archaeological site is a Quetta Miri (a mass of indurate clay). The base of Miri is 183 meter long by 122 meter wide and rises 24.4 meter above the plain. The Miri is now used as an Arsenal. Among other noticeable mounds are one between Katir and Kuchlak, known as the Kasiano Dozakh, Tor Ghund near Baleli and Tor Wasi between Panjpai and Muhammad Khel. Besides, some karezes of archaeological interest are found at Kirani, Sariab and Kachi Baig.

In March 1883, the Khan of Kalat leased Quetta to the British authorities. In April 1883 it was combined with Pishin into a single administrative unit. At that time Sir H.S. Barnes was appointed as the first Political Agent. The administrative situation remained till the partition of the sub-continent in 1947. Quetta and Pishin continued to be a single administrative unit till 1975. In that year Pishin was made a separate administrative unit. Now the district consists of two sub-divisions (I) Quetta city (ii) Quetta Sadar. The district also comprises one Tehsil (Quetta) and one Sub-Tehsil (Punjpai).