The initial planning for the new cathedral was carried out by Father Trevis, who was once again assigned to St Margaret's after Cosgrove was named bishop. The assignment became too much for him, however, and he was replaced by the Rev. James Davis. James J. Egan, an architect from Chicago, was chosen to design the new cathedral. At the same time, he also designed St. Ambrose Church in Des Moines, which became a cathedral in 1911. The Ecclesiological Society, which had a mission of preserving Gothic architecture, was an influence in the church design. The cathedral was built on the English parish church model. Walsh & Edwards of Davenport were chosen to be the contractor, and Davenport architect Victor Huot as supervising architect.