Anchoring Milwaukee's Yankee Hill neighborhood is the imposing St. Paul’s Episcopal Church. Built in 1882, this church is listed in the National Register of Historic Places and is one of Milwaukee's notable examples of Richardsonian Romanesque architecture — a style popular in the late 19th century.
But the building's story goes back about a billion years to a period of intense volcanic activity, when what is now North America was being ripped apart.
Raymond Wiggers, architectural geologist and author of Milwaukee in Stone and Clay, joined Lake Effect's Sam Woods to discuss the building's hidden history for the latest episode of What Milwaukee is Made Of.
Out of a continental rift, a stone is born
St. Paul’s outer exterior features an elegant dark red stone. This stone is called Lake Superior brownstone, quarried out of Basswood Island in Michigan’s Upper Peninsula and the Apostle Islands area of northern Wisconsin.
But about a billion years ago, this area was part of a giant continental rift stretching in a horseshoe shape from modern-day Nebraska to Ohio. Wiggers says this rift was the site of constant volcanic activity.
“It created this big area where a lot of magma from deep in the Earth’s interior came welling up to the surface and erupting,” Wiggers said. “These were like lava fountains that were spewing out over a long distance.”
When this volcanic activity ceased, this stone formed from sand sliding into the belly of the rift.
“It filled in that low area,” Wiggers said. “What you’re seeing if you go up to side the church ... you’ll see lots of sand grains coated in [rust], and larger pebbles that were washed down the side of the rift.”
Life on Earth at this time was sparse, but present.
“At the very least, you had not only bacterial life, but algae,” Wiggers says. “But if you had been in northern Wisconsin ... it would’ve been a much more barren landscape than there is now.”
Bushkill slate: an avalanche aftermath
The stone used for the roof of this church is called Bushkill slate by geologists and marketed as “Chapman slate.” It is sourced from eastern Pennsylvania and was born about 465 million years ago.
The slate is a metamorphic rock, meaning it used to be something else before taking its present form.
“It formed from submarine avalanche deposit rolling down into what was then the ocean,” Wiggers says. “Eventually, when there was continental collision later, it was hardened and compressed into this slate material which is so wonderful for roofing tile.”
An American take on a European classic
St. Paul’s is one of Milwaukee’s premier examples of the Richardson Romanesque style, along with the Pfister Hotel and downtown federal courthouse. The style was created by Henry Hobson Richardson.
Wiggers says Richardson’s style is a 19th-century American twist on old European design.
“I think it was Richardson’s own idiosyncratic way of looking at what the Medieval style had been,” Wiggers says. “It has a particularly robust, rugged look to it, which I think was more characteristic of the American psyche at the time.”
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