Macdonell's home, known as Poplar Villa, is a graceful adaptation of the Palladian style. It served as a centre for his milling, general merchandising, warehousing and freight-forwarding business.

Using the commercial instincts he had honed in the competitive fur trade, Macdonell opened a general store in Pointe Fortune, served as a freight forwarder in the movement of goods from his property to Lachine, near Montreal, and sponsored the building of the Ottawa – the first steamboat on the Ottawa River. He also made noteworthy contributions to the region's public life as a judge in the Ottawa district (1816-25), and later as a member of the Upper Canada House of Assembly. Macdonell died in Pointe Fortune in 1850.

In 1882, the Williamson family bought the house. It remained in the Williamson family until the early 1960s. The Ontario Heritage Trust acquired it in 1978 to save it from demolition, and conducted extensive architectural and archaeological investigations on the property.

Seasonally open to the public, the site is operated by the Friends of Macdonell-Williamson House/Les Amis de la maison Macdonell-Williamson under a custodial agreement with the Trust.