Kirby moved in 1832 to the United States and in 1839 to Canada, where he settled in Niagara and became editor of the Niagara Mail (1850–71) and collector of customs from 1871 to 1895. Kirby was a fervent loyalist (favouring retention of Canada as part of the British Empire) and in the 1840s wrote several works that are intensely pro-British in sentiment. Topical history was treated in his Annals of Niagara (1896), a solid historical work, and in his verse epic The U.E.: A Tale of Upper Canada in XII Cantos (1859). Kirby also corresponded with many prominent literary and political figures in England and Canada.

Kirby's masterpiece, The Golden Dog: A Legend of Quebec, contains good characterization and detailed description of rural and urban locations. Historical information and materials from French Canadian legend are fused into a skillful plot dealing with the British conquest of Quebec in the 18th century.