[7] Onitsha slowly grew to become an important trading port for the Royal Niger Company in the mid-1850s following the abolition of slavery and with the development of the steam engine when Europeans were able to move into the hinterland.

[18] The British colonial government and Christian missionaries penetrated most of Igboland to set up their administration, schools and churches through the river port at Onitsha.

This has helped to grow trade routes with western Nigeria and created significant economic linkages between Onitsha and Benin City and Lagos particularly.

Nowadays, it is a way for the people of Onitsha to keep their culture alive, take stock of the communal activities and it has become a major event that draws visitors from far and wide to the city.

These factors have historically and in modern-day made Onitsha into major trading center between the coastal regions and the north, as well as between eastern and western Nigeria.

Saharan harmattan winds are experienced during the winter months, causing haze and poor visibility with thunderstorms common in March/April as well as in late September/October.

In the early 1960s, before the Nigerian Civil War (see also Biafra), the population was officially recorded as 76,000, and the town was distinctive in a number of dimensions; the great Nigerian writer Chinua Achebe (born and raised in the contiguous town of Ogidi) characterized it as harboring an "esoteric region from which creativity sallies forth at will to manifest itself," "a zone of occult instability" (see "Onitsha Matters").

[27] However, infrastructure has not kept pace with urbanization and haphazard building practices without zoning regulations has left in its wake a chaotic and congested city rife with lawlessness.

[36] The Onitsha writings have two distinct characteristics: a fascination with westernized urban life and the desire to warn the newly arrived against the corruption and dangers that accompany it.

Typical titles are “Rose Only Loved My Money,” “Drunkards Believe Bar as Heaven,” “Why Some Rich Men Have No Trust in Some Girls,” and “How to Get a Lady in Love.” Sentimental novelettes, political tracts, and “how to” guides on writing love letters, handling money, and attaining prosperity all have achieved great commercial success, and booksellers hawk these cheap, locally produced pamphlets (which are printed on handpresses) at Onitsha.

The amount of waste generation is attributed to the city's high population being a commercial area that draws in people from within and outside Nigeria for business purposes.

Onitsha is twinned with: The Onitsha people were among the first Igbo to embrace western education,[43] producing notable people like Bishop Alphonsus Chukwuma Onyeabo, Order of the British Empire, 1879–1954, and the main contributor of the English to Igbo bible,[44] Dr. Nnamdi Azikiwe, Owele of Onicha, Zik of Africa, and the first president of the post-independent Nigeria.