[2] His father, Henry Sieck, was a Lutheran minister and president of St. John's College in Winfield, Kansas, from 1893 to 1895.
[2] At the 1933 annual Lutheran convention at Concordia Seminary, he spoke of the need for the church to preach and teach rather than focus on the secular.
In 1943, Sieck left Zion Lutheran Church to become the president of Concordia Seminary following the end of Ludwig E. Fuerbringer's tenure.
[2] Sieck and fellow Lutheran minister Alfred Doerffler were reportedly briefly involved in the events now known as exorcism of Roland Doe in 1949.
[7][8] At the time of his death, Sieck was chairman of the National Advisory Emergency Planning Council of the Evangelical Lutheran Conference.