James Dunn became involved in the legal aspects for underwriting activities for companies being listed on the Montreal Stock Exchange and in 1902 he established the J.H. Dunn & Co. stock brokerage company. With $20,000.00 borrowed from his father-in-law, he acquired a seat on the stock exchange. Canadian business at the time was still heavily dependent on investment money from the British financial markets and Dunn became an expert at raising foreign capital for the underwriting of securities as well as selecting the right places to invest. Articulate, outspoken, and with a personality that commanded respect, Dunn had already made contacts with a number of influential people, including a number of railroad executives, one of the most powerful group of entrepreneurs of the day.