The company was officially formed on 10 March 1949 under the name Macneill & Barry Limited. It started its business as general merchants, agents, and manufacturers of various products. Over time, the company grew into a multi-division business involved in manufacturing tea, jute, engineering items, and reprographic products. It also had agency and trading divisions.

A major milestone came in 1975, when Williamson Magor & Co. Limited, a well-known company in the tea industry, merged with it. After the merger, the company’s name changed to Macneill & Magor Limited. Williamson Magor & Co. Limited had been in the tea business since 1868 and was one of India’s tea pioneers. The merger made the company a major tea producer while still running other businesses. Later, the company changed its strategy and separated all non-tea divisions, transferring them to newly formed group companies.

In return for transferring these businesses, the company received a large number of shares from the new companies. After completing this process, the company changed its name again in 1992 to Williamson Magor & Co. Limited. Its main activities then became tea production and investments in group companies. Eventually, the tea business was also transferred to other group companies, turning the company into a pure investment and holding company.

The company applied to the Reserve Bank of India (RBI) to be registered as a Non-Banking Financial Company (NBFC). It received the NBFC license on 31 March 2003, and since then, it has been operating as a financial investment company with major holdings in companies like McLeod Russel India Limited, Eveready Industries India Limited, Kilburn Engineering Limited, McNally Bharat Engineering Company Limited, and others.

The company is listed on the Bombay Stock Exchange (BSE), National Stock Exchange of India (NSE), Calcutta Stock Exchange, and the Guwahati Stock Exchange.

The company owns a 10-storey building at Four Mangoe Lane, Surendra Mohan Ghosh Sarani, Kolkata 700001, which houses its registered office. As the main holding company of the group, it is widely known as part of the Williamson Magor Group (WM Group).