In 1849, the Clementson family emigrated from England to the United States, settling in Hazel Green, Wisconsin.

[1] His father was a wheelwright and wagonmaker, and Clementson worked in his shop as a young man.

Clementson was admitted to the State Bar of Wisconsin in 1868, and later that year he was elected district attorney for Grant County.

He defeated incumbent Judge Montgomery Morrison Cothren and was subsequently re-elected six times, dying in office in 1920.

Mary was a niece of his law partner, J. Allen Barber, and a descendant of Aaron Burr.