Naomal Hotchand (a controversial character because of his relationship with the British) whose memoirs are a valuable source wrote that in the early 18th century
his great-grandfather Bhojoomal moved to Kharakbunder (bunder= port) to the west of Karachi at the mouth of

the river Habb. According to Naomal, Kharakbunder was 'great in commercial renown'. 'Bhojoomal had his own separate goomashtas' [agents] at Sonmiani, Gwadur, Beyla, & Muscat. The agent at Muscat opened branch firms at Bushire, Shiraz and Bahrein.

In the course of time branch firms were established at Shah
Bunder and Lahori-Bunder, then two important sea port towns in Sind, & trade with Surat, Porebunder and Malabar was carried out extensively.'

However, Kharakbunder silted up & Bhojoomal & a group of other merchants moved to Karachi, having identified the Karachi creek as suitable for their purposes. 'There stood at the head of the bar about 20 to 25 huts of fishermen. The spot was then called Dirbo.'

Around 1729 the people of Kharakbunder settled in Karachi to an area then known as (Kalachi-jo-ghote or Kolachi-jo-ghote). The area was then under the control of the Kalhoras & then after 1783 the Talpur mirs, a Baloch dynasty.

Sindh has had mercantile connections to scattered parts of the world since much before colonial rule. A good book to read on this is Claude Markovits's 'The global world of Indian merchants'. https://www.cambridge.org/core/books/global-world-of-indian-merchants-17501947/5EECD4745021DEA9D35F8CB619DBF239

In 1832 the manager of Naomul's Calcutta branch Nibhoomal Motoomal (I do love their names) bought a European ship & put it under an English captain. The ship plied between ports in Java, China & the Malabar coast & Bombay.

Karachi was still a fishing village when Napier annexed Sindh in 1843 but the port was growing in importance. In 1878 Karachi overtook Calcutta as India's major wheat exporter and by the end of the 19th C was India's 4th major seaport

(See Evans gazetteer of 1907 & Cheesman's
'Landlord power & rural indebtedness in colonial Sind') as sources for the above.

Migrants from other parts of Sindh, the Bombay Presidency (of which Sindh was a part) & further afield began to come to Karachi which was growing in size and importance.

In fact, Markovits suggests, competition from other mercantile communities in Karachi had strengthened Sindwork merchants’ links to Bombay who tried to ‘bypass’ Karachi for Bombay (Shikarpuri merchants & bankers appear to have done better in Karachi).

The Amils, who were more often employed in the professions and as government servants (these were not rigid distinctions) were behind the founding of Dayaram Jethmal College (DJ Sindh College), at the time the most prominent educational institution in Sindh.

Parsis and Khojas were amongst the other mercantile communities invested in Karachi. Rustom Sidhwa was a prominent Sindhi Parsi who became a part of the Indian Constituent Assembly.

Karachi became a polyglot city. Sarah Ansari notes that Gujarati became the lingua-franca of parts of the city during the inter-war period. According to the 1941 census Sindhi was spoken as mother tongue by 61.2% of the population. In 1951 this figure was 8.6 %.

Of course census figures from the war years weren't completely reliable but we have to be careful when taking about 'majorities' at that time (ethnocentric twitter of all shades please note). See Ansari: Pakistan's 1951 Census: State-Building in Post-Partition Sindh

Karachi was Sindh’s capital before partition (i.e. between separation from the Bombay Presidency in 1936-37 & 1948). Before this it had local municipal government-Harchandrai Vishandas,

the modernising mayor of the Karachi municipal council (1911-21), pushed the building of new roads and parks and perhaps not so sensibly had the course of the river Lyari changed.

Because it already had an existing infrastructure including a newish legislative assembly building, banking networks, educational institutions and an airport it was chosen as Pakistan’s capital.

The airport was necessary because of the need to connect to East Pakistan. Many of Sindh's Hindus and Parsis left at partition (this included the business elite and the literati). Ansari cites sources which estimated that the amount that left Sindh was between 20-30 crores:

(Ansari, Life after partition). There were other groups of people who suffered a lot more at this time. Faced with the departure of economically significant minorities, the Sindh government enacted laws to prevent them from leaving.

which included powers to arrest the most vulnerable of the refugees from the lowest castes who worked as sweepers and sanitation workers.

Many of them were migrants from other parts of India such as Kathiawar, UP, & as far afield as Andhra. Fearing the breakdown of sanitation in the city if they left the new government of Pakistan actively prevented them from leaving (this included arresting them).

The Indian government took its own sweet time to respond to these crises. I am writing about this aspect of partition in more detail to be published later. But in sum: Karachi did always have different communities, it was indeed the capital of Sindh until 1948 and all those who

live in it and belong to it now should maybe stop fighting about this history and see what they can do for its many different communities, some very vulnerable, together? All us South Asians are in a very bad place and need to come to a point of reconciliation and to do better.

NB: The reference to crores leaving Sindh is to rupees not people.