In 1899, J.S. McLennan developed plans for the construction of the Petersfield estate, located on Amelia Point across the harbour from the Sydney Steel Plant. The McLennans purchased the land, originally settled by Loyalist immigrants from the United States, down to the waterfront, and by 1902 the estate was finished. The architectural style of the home was of the Italianate design, popular among the Boston elite.

The early years at Petersfield were exceedingly happy ones for the McLennans. The family traveled extensively and, in turn, entertained their friends at Petersfield. Photographs and the guestbook from this era show that the McLennans were host to tea parties, boat races, skating parties, and horse-drawn sleigh rides for a wide range of friends and guests. Louise managed the household and presided over events, which Katharine would later imitate, though on a smaller scale, when Petersfield became more a place of repose for J.S. in his later years.

After J.S. died in 1939, Katharine was left to manage Petersfield on her own. She tried to maintain the home as it was in earlier times, but the structure often needed work. One day in January of 1941, Katharine saw men taking a survey of her land and the waterfront and discovered that the federal government planned to expropriate Petersfield for use as a naval base. Unable to stop the government’s plans, Katharine was forced to abandon the estate, moving to 49 Whitney Avenue in Sydney where she would reside for the rest of her life. At the end of the World War II, Petersfield was of no further use to the government and the buildings were allowed to deteriorate to the point where they had to be destroyed.

Reconstruction of the former estate was debated for a number of years but the cost of such a project was too high. The beauty of Petersfield, however, has been maintained to this day, as the site has been converted to a provincial picnic park and is enjoyed by patrons year round.