By 1958, the firm had developed a large network of branches including locations in every major Canadian city as well as international offices in New York, Boston, Philadelphia, and London. The late 1950s saw Dominion Securities fully involved in the trading of securities on the secondary markets as members of The Toronto, Montreal, Winnipeg, and Canadian Stock Exchanges, as well as affiliate members of the American Stock Exchange. They also had access to the NYSE and numerous other exchanges at the time. During this period, DS maintained a head office at 50 King Street West in Toronto and was headed by President G.E. Phipps, Chairman G.P. Rutherford, and Vice-chairman, H. N. Bawden.