Drilling uncovered iron ore, and in 1879 the company opened the Cliffs Shaft, then known as the "New Barnum".

[3] The mine was at one time the nation's largest producer of hematite, and shipped ore every year but one from 1887 until its eventual close.

[2] The Cliffs Shaft mine complex was listed on the National Register of Historic Places in 1992.

[6] Above ground, the Cliffs Shaft site covers 15 acres and includes three headframes and eight other buildings.

The two 1919 headframes, mirror images of each other,[7] are unusual as a collaboration between mining engineers and a professional architect.

[7] When Cliffs Shaft engineers presented company president William G. Mather with proposals to update the headframes, Mather suggested that, because of the prominence of their location, the headframes combine practicality with architectural beauty.

The positions of interior beams were largely determined by available openings in the wooden headframes being built around.

Visitors can see mining artifacts, photographs and equipment, as well as a chemical lab, blasting items, and the engine house with its air compressor room.