Duncan Rule (1856-) served Cerro Gordo County as the clerk of court. He married Huldah Thompson in 1881. Duncan was one of the charter members of Mason City Lodge K. of P.

In 1889, John Cliggitt and Ducan Rule formed the law firm of Cliggitt and Rule. It was successful and later became the firm of Cliggitt, Rule, Keeler & Smith.

The Duncan Rule house was designed by Mason City architect E. R. Bogardus who utilized a shingle-style design. The house was placed in the National Register of Historic Places on October 16, 1979.