The Humayun family's trading legacy traces its origins to the early 1950s, when the late A.Z. Humayun founded his eponymous firm A.Z. Humayun & Co., one of the largest importers & distributors of coal in the erstwhile united Pakistan.

The firm imported coal from leading international suppliers through chartered ocean-going vessels. Upon arrival in the Bay of Bengal, the cargo was transshipped from mother vessels into smaller inland bulk carriers and transported to the company's own river terminal at Aliganj, Narayanganj. From there, coal was distributed throughout East Pakistan. Simultaneously, consignments destined for West Pakistan were discharged at the Port of Karachi, where the company's West Pakistani agents managed their distribution across the western wing of the country.

A.Z. Humayun & Co. remained a prominent participant in Pakistan's coal trade until 1971. Following the Liberation War and the independence of Bangladesh, the company's coal terminal in Narayanganj was requisitioned by the government, bringing the operations of the original trading house to an end.