The Union Bank of Halifax was granted a charter by the government of Canada in 1856 and established its head office at the corner of Hollis and Prince Streets in the port city of Halifax, Nova Scotia.

The driving force behind the bank, and its first chairman, was Halifax businessman and former mayor, William Machin Stairs (1789-1865). Amongst the Bank’s other founders was John William Ritchie who served as director until 1866.

Recognized for the quality and fraternity of its employees, Izaak Walton Killam began his business career in his hometown of Yarmouth, Nova Scotia as a junior clerk at the local branch of the Union Bank of Halifax.

In the nine years he was in charge, William Machin Stairs began an expansion of the bank that his successors continued. The Union Bank developed a strong regional branch network as well as offices in Trinidad and Puerto Rico that served the bank’s clients with shipping and trading interests throughout the Caribbean.

However, by the turn of the century, Toronto, and particularly Montreal, were becoming the financial center for all of Canada. The Union Bank's executive at the time failed to recognize the need for expansion into the growing national market. Within a few years, increased competition from much larger financial institutions meant a merger with another financial was essential if the bank was to survive. As such, in 1910, the board of directors of the Union Bank of Halifax accepted a takeover offer from the Royal Bank of Canada, then the country's third-largest bank.