Lannon Stone

Lannon stone is the buff building stone of southeastern Wisconsin, the material a great deal of Milwaukee is faced in, and it is not the limestone it is usually called. It is a dolomite, and that distinction is not pedantry: it is the reason the stone outlasted the limestones it competed with.

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It is a dolomite, and that is why it lasted

Limestone is calcium carbonate. In dolomite, magnesium has replaced a large share of that calcium, and the resulting mineral is harder and markedly less soluble in weak acid. Rain is a weak acid. So a dolomite wall in a cold, wet, road-salted climate holds its arris and its face where a soft limestone would round off and sugar.

The Wisconsin Historical Society is blunt about the naming, describing the county's stone as "high grade limestone, actually dolomite". The trade kept the older word because that is what it was sold as in the 1850s, and the name stuck.

That makes Lannon the third stone in this library whose trade name misdescribes the rock, and in each case the name is reporting behavior rather than mineralogy. Tennessee Pink Marble is a limestone that polishes like a marble. Stony Creek Granite is a gneiss that cuts like a granite. Lannon is a dolomite that was sold as limestone because limestone is what a buff sedimentary building block was called.

Where it comes from

The stone belongs to the Niagara Escarpment, the long Silurian dolomite ridge that curves under the Great Lakes from New York through Ontario and down into Wisconsin. It formed in a warm shallow sea more than 400 million years ago, and in the Lannon and Sussex area of Waukesha County it sits close enough to the surface to be worked from shallow open quarries rather than mined.

The name is not geological. It comes from William Lannon, one of the original settlers of the village that took his name, and the stone took the village's.

From paving stone to veneer

The trade is old and its shape has changed twice.

By 1855, at least a dozen quarries were carting Lannon stone into Milwaukee, mostly as paving stone. By the early 1890s around fourteen quarries were working the belt, producing paving, curbing, flagging and building stone. Through that period it was a structural material: solid stone walls, laid full thickness.

After the Second World War the market changed. Load-bearing stone walls gave way to frame construction, and Lannon stone became a facing material instead, cut as thin veneer, or sold as ornamental landscape rock. That is still the bulk of the trade today.

Both eras are visible on the ground, which is the useful part for anyone matching existing work: a pre-war Lannon wall is likely to be full-bed and structural, a post-war one is likely to be a veneer over frame.

What it was prized for

Uniformity, hardness and color, in that order. Lannon splits into flat, blocky, roughly rectangular pieces along its bedding, which makes it fast to lay and forgiving of a mason working to a coursed or broken-coursed pattern. The buff runs consistent enough across a quarry face that a large elevation reads as one material, which is genuinely uncommon in a natural stone and is why it was specified across whole subdivisions.

The consequence for a buyer is the reverse of most stone advice. With Lannon you are not usually hunting for the interesting block. You are relying on the stone being predictable, and specifying by collection and coursing pattern rather than hoping for movement.

Where you have already seen it

It became the predominant material for houses and churches across Milwaukee, Chicago and the northern Midwest through the post-war building boom, which is why so much of the region's mid-century domestic architecture shares one palette. Larger projects attributed to the Lannon-area quarries include Milwaukee's main post office, the Milwaukee County Museum, the Milwaukee County Zoo and Mayfair.

Applications

Building veneer and full-bed walling: the core of the trade. Available as full-bed stone for structural and heritage work, and as thin cut veneer where the wall behind is frame.

Landscape and retaining walls: the post-war growth market, in wallstone, outcropping and boulder sizes.

Flagging and paving: the original nineteenth-century use, and the stone splits naturally into flat pieces that suit it.

Steps, treads and coping: cut to size, and hard enough at Mohs 3.5 to 4 to take the traffic.

Sills, caps and signage: dimensional pieces, where the uniform color matters most.

Heritage restoration: a great deal of pre-war Milwaukee is built in it, and matching means going back to the same belt.

Buying it

Halquist Stone at Sussex is the established quarrier, working since 1929 and quarrying at Lannon, Chilton and Fond du Lac. It is a member of the Natural Stone Institute, which is what carries the Verified badge here, and it supplies both full-bed and thin veneer across seven veneer collections.

Two things worth knowing before ordering. Decide full-bed or thin veneer first, because it changes the wall detail, not just the price, and a thin veneer cannot be used to patch a structural wall. Specify the collection and the coursing, since with a stone this uniform the pattern does more visual work than the stone does.