Karachi
British control

The British East India Company captured Karachi on 3 February 1839 after HMS Wellesley opened fire and quickly destroyed Manora Fort, which guarded Karachi Harbour at Manora Point. Karachi's population at the time was an estimated 8,000 to 14,000, and was confined to the walled city in Mithadar, with suburbs in what is now the Serai Quarter. British troops, known as the "Company Bahadur" established a camp to the east of the captured city, which became the precursor to the modern Karachi Cantonment. The British further developed the Karachi Cantonment as a military garrison to aid the British war effort in the First Anglo-Afghan War.

The Portuguese Goan community started migrating to Karachi in the 1820s as traders. The majority of the estimated 100,000 who came to Pakistan are primarily concentrated in Karachi.

Sindh's capital was shifted from Hyderabad to Karachi in 1840 when Karachi was annexed to the British Empire after Major General Charles James Napier captured the rest of Sindh following his victory against the Talpurs at the Battle of Miani. Following the 1843 annexation, on 17 February the entire province was amalgamated into the Bombay Presidency for the next 93 years, and Karachi remain the divisional headquarter. A few years later in 1846, Karachi suffered a large cholera outbreak, which led to the establishment of the Karachi Cholera Board (predecessor to the city's civic government).

The city grew under the administration of its new Commissioner, Henry Bartle Edward Frere, who was appointed in the 1850s. Karachi was recognized for its strategic importance, prompting the British to establish the Port of Karachi in 1854. Karachi rapidly became a transportation hub for British India owing to newly built port and rail infrastructure, as well as the increase in agricultural exports from the opening of productive tracts of newly irrigated land in Punjab and Sindh. By 1856, the value of goods traded through Karachi reached £855,103, leading to the establishment of merchant offices and warehouses. The population in 1856 is estimated to have been 57,000. During the Sepoy Mutiny of 1857, the 21st Native Infantry, then stationed in Karachi, mutinied and declared allegiance to rebel forces in September 1857, though the British were able to quickly defeat the rebels and reassert control over the city.

Following the Rebellion, British colonial administrators continued to develop the city's infrastructure, but continued to neglect localities like Lyari, which was home to the city's original population of Sindhi fishermen and Balochi nomads. At the outbreak of the American Civil War, Karachi's port became an important cotton-exporting port, with Indus Steam Flotilla and Orient Inland Steam Navigation Company established to transport cotton from rest of Sindh to Karachi's port, and onwards to textile mills in England. With increased economic opportunities, economic migrants from several ethnicities and religions, including Anglo-British, Parsis, Marathis, and Goan Christians, among others, established themselves in Karachi, with many setting-up businesses in the new commercial district of Saddar. Muhammad Ali Jinnah, the founder of Pakistan, was born in Karachi's Wazir Mansion in 1876 to such migrants from Gujarat. Public building works were undertaken at this time in Gothic and Indo-Saracenic styles, including the construction of Frere Hall in 1865 and the later Empress Market in 1889.

With the completion of the Suez Canal in 1869, Karachi's position as a major port increased even further. In 1878, the British Raj connected Karachi with the network of British India's vast railway system. In 1887, Karachi Port underwent radical improvements with connection to the railways, along with expansion and dredging of the port, and construction of a breakwater. Karachi's first synagogue was established in 1893. By 1899, Karachi had become the largest wheat-exporting port in the East. In 1901, Karachi's population was 117,000 with a further 109,000 included in the Municipal area.

Under the British, the city's municipal government was established. Known as the Father of Modern Karachi, mayor Seth Harchandrai Vishandas led the municipal government to improve sanitary conditions in the Old City, as well as major infrastructure works in the New Town after his election in 1911. in 1914, Karachi had become the largest wheat-exporting port of the entire British Empire, after large irrigation works in Sindh were initiated to increase wheat and cotton yields. By 1924, the Drigh Road Aerodrome was established, now the Faisal Air Force Base.

Karachi's increasing importance as a cosmopolitan transportation hub leads to the influence of non-Sindhis in Sindh's administration. Half the city was born outside of Karachi by as early as 1921. Native Sindhis were upset by this influence, and so on 1 April 1936, Sindh was established as a province separate from the Bombay Presidency with Karachi was once again made capital of Sindh. In 1941, the population of the city had risen to 387,000.
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