Sexauer was born in Kingston, Illinois and came to New York in 1914. In 1915 he purchased a farm outside of Auburn, N.Y. Soon after starting farming, he became active in a local cooperative, and in 1919 became a director of the Dairymen's League's Cooperative Association (now Dairylea, Inc.). In 1921 he was elected to the League's executive committee and in 1928 became President. During the Roosevelt administration, he played an active role in the Committee for the Nation and the Committee for Constitutional Government.