In 1857, John Redpath's eldest son, Peter, became a partner; his brother-in-law, George Alexander Drummond, joined the firm in 1861.

Unable to compete with the giant low-cost producers in the United States, for the three years between 1876 and 1878, the company ceased operations.

Following the tariff protections implemented under the National Policy by the government of John A. Macdonald, the company reopened in 1879, as did St. Lawrence Sugar, a new competitor established in Montreal.

Under his guidance, the company's success allowed for construction of a new six-storey plant built on the existing site, doubling production capacity.

The Redpath Sugar Refinery was built on the Toronto waterfront in the late 1950s, at the time of the completion of the Saint Lawrence Seaway, and it is still in operation.