Born in modest circumstances in 1885 at Yarmouth, Nova Scotia, Izaak Walton Killam began his business career at the age of 18 as a junior clerk in the Yarmouth branch of the Union Bank of Halifax. He was soon transferred to the Bank's head office in Halifax, where his talent and reputation caught the attention of Max Aitken (later Lord Beaverbrook), who was in the process of setting up the Royal Securities Corporation. In 1904, Aitken persuaded Mr. Killam to join Royal Securities, which became the foundation of Mr. Killam's remarkable financial career. By 1914, Mr. Killam had replaced Lord Beaverbrook as president of Royal Securities, and soon after acquired Beaverbrook's shares in the firm. For 40 years, Mr. Killam served as president of Royal Securities; in that time, the company became one of Canada's most influential investment houses and Izaak Walton Killam established himself as one of the outstanding figures in Canadian financial history.

Recognizing the great potential of Canada's forest and electric power industries, he organized many new companies and modernized others in these fields. The various Royal Securities holdings included power companies in Alberta, Ontario, Nova Scotia and Newfoundland, as well as pulp and paper companies in British Columbia and Nova Scotia. There were other interests as well, such as Moirs Limited of Halifax, which became one of the best-known chocolate companies in Canada.

Notwithstanding his prodigious financial accomplishments, Izaak Walton Killam was a very reserved man who eschewed publicity and was virtually unknown ouside a very small circle of close acquaintances. True to his namesake, Izaak Walton, he was an ardent salmon fisherman throughout his life. He shared with his wife, Dorothy, a passion for baseball, especially the Brooklyn Dodgers. Characteristically, the substantial contributions he made to charities throughout his lifetime were always given anonymously.