After establishing a solo practice in the early 1960s, Haertling explored the possibilities of Neo-Expressionist architecture, seeking inspiration from the natural world, and pushing the boundaries of modern architecture. St. Stephen’s Lutheran Church, with its swooping lily-like shape—made possible through the use of thin-shell concrete engineering techniques and the expertise of engineer Ib Falk Jorgensen—exemplifies Haertling’s unique design philosophy and is the first of his projects to be listed in the National Register of Historic Places.