arza clair casselman was born january 19, 1891 in mariatown, ontario, located in what was then williamsburg township (now, the municipality of south dundas) in the united counties of stormont, dundas and glengarry. casselman was the son of michael and almeda casselman, who were married in 1872. his mother almeda was born in williamsburg township in 1851 and his father michael was born in matilda township in 1848, now also part of south dundas. his family was likely descended from the first casselmans to settle in dundas county, who arrived in canada around 1784 from the mohawk valley, new york, as united empire loyalists. casselman's father michael was also involved in politics, but at the municipal level. michael casselman was elected to the stormont, dundas and glengarry counties council in 1899 and was chosen as counties warden in 1903. witnessing his father being actively engaged in local politics perhaps had some influence on a. c. casselman's future political interests.