Mary Agnes Thompson was born in March 10, 1872 on Amherst Island, Ontario. She was the daughter of Archibald Thompson and Eliza Dunning, both from Ireland. Records show she had one sister and nine brothers. Mary married John Wilson in Deseronto, Ontario on November 1, 1898. The witnesses to the wedding were her brother Cecil and her sister Agnes. The Thompson family seems to have moved to Deseronto sometime between 1891 and 1898 since they were still living on the island in the 1891 census. John and Mary lived on Howe Island, Ontario for the first 5 or so years of their marriage.