[6] Sumitomo Corporation was incorporated in December 1919 as The Osaka North Harbour Co., Ltd. to engage in real estate management, land reclamation, land grading, harbor repair construction and related work in the Osaka northern harbor region.

[7] Sumitomo Building transitioned to general trading, looking to handle products from Japan's major manufacturing firms in various industries, and changed its name to Nippon Engineering Co., Ltd. (Nihon Kensetsu Sangyo Kaisha), starting a new existence as a general trading firm with a sales staff of just 32 people.

By the 1960s Sumitomo officially aimed to be one of the "Big Three" general trading companies, alongside Mitsubishi and Mitsui.

The company's president, Kuniharu Nakamura, attributed these losses to both adverse market factors and Sumitomo's relative inexperience in the field.

As a result of these setbacks, Sumitomo was overtaken by Itochu as Japan's third-largest general trading company.

[9] Berkshire Hathaway acquired over 5% of the stock in the company, along with four other Japanese trading houses, over the 12-month period ending in August 2020.

[13] Sumitomo, along with Mitsubishi Heavy Industries, worked with the Department of Transportation of the Philippines for the rehabilitation of the MRT Line 3 in Manila from 2019 to 2021.