 In 1940, he resigned to become president of the Ottawa Electric Company.He also had his own firm, Rowatt-Ahearn Ltd. and became president of the Ottawa Electric Railway Company in 1938 after his father died.Ahearn also had interests in several other Ottawa businesses including Wallace Realty Company, the Ottawa Car Manufacturing Company, the Ottawa Gas Company, the Ottawa Investment Company, Ahearn & Soper and other businesses.