We have spent several weeks reading the original architects’ drawings for the Charles S. Pillsbury Mansion floor by floor — the first floor, the second, the basement, and the grounds. Every one of those is a plan: the house sliced horizontally and looked at from above.

Sheet No. 12 does something different, and it is the most revealing drawing in the set. It is a section — the house sliced vertically, straight through, and looked at from the side. Everything the plans show one storey at a time, this shows all at once.

What the sheet actually says

The title block reads, in the careful hand-lettering of the period: Residence for Mr. C. S. Pillsbury, North East Cor. 1st Ave. S. & 22nd St., Minneapolis, Minn. The drawing itself is labelled Transverse Section, at a scale of a quarter inch to the foot. The firm block in the opposite corner reads Hewitt & Brown, Architects – Engineers, 716 4th Ave. South, Minneapolis, and the sheet is numbered 12.

The address is worth a pause. The drawing locates the house at the north-east corner of First Avenue South and 22nd Street; the Club’s address today is 100 East 22nd Street. Both describe the same corner. We are noting the difference rather than smoothing it over — period drawings should be read, not translated.

Why a section is the drawing that explains a house

A plan tells you how rooms sit beside each other. An elevation tells you what the outside looks like. A section tells you how the building works — how tall the rooms are, how the floors are carried, how the stair climbs, what is above the ceiling and below the floor.

On Sheet No. 12 you can count the house from the ground up in a single glance: the basement, the first floor, the second, the third, and the roof over all of it. The stair is drawn in profile, treads stepping up through the middle of the house, so you can see for the first time how the levels actually connect rather than merely that they do.

The steel is the surprise

The most interesting annotation on the sheet is a single word, written twice, with a fine leader line pointing at the end of a floor beam: “Channel.”

That is a structural note. A channel is a rolled steel section, and where the floor lines are drawn you can also make out the unmistakable I-shaped profile of steel beams set into the hatched floor construction. This is a house that reads, from the outside, as an English manor of great age — and the section shows the modern skeleton underneath it. The firm signed the block “Architects – Engineers,” and this drawing is where the engineering half of that title becomes visible.

It is a useful corrective to the way the mansion is usually described. The splendors — the centuries-old English interiors, the carved oak, the imported fireplaces — are genuinely old. The building that holds them was, in 1916, thoroughly modern.

Reading down from the roof

At the top of the section, above the third floor, the architects drew a raised monitor with a skylight in it — a lantern set into the roof to bring daylight down into the middle of the plan, where no window could reach. A tall chimney rises alongside it, drawn in elevation rather than cut, so you see its cap and courses.

At the other end of the drawing, at ground level, are the notes that never make it into a photograph: broken stone laid against the foundation, and a four-inch tile drain running along the footing. A house of this size on this ground had to be kept dry, and the architects said so on the drawing.

Between those two extremes are the ceiling heights, dimensioned in feet and inches beside each storey. They are the numbers that explain why the principal rooms feel the way they do when you walk into them, and why the third floor feels different again.

What the drawing does not settle

It does not give a completion date. The sources on this house disagree about when it was finished, and a sheet from the working set is not the place to resolve that; we have declined to assert a year in these posts and continue to decline. What Sheet No. 12 gives instead is something better than a date: the house as its designers understood it, in one vertical slice, before a single stone of it existed.

More on the design and the firm is on our pages about building the mansion and the owners. The wider story of the industry that paid for it is told at the Mill City Museum, and the mansion’s listing sits within the National Register of Historic Places.

Come and stand inside the section

The pleasure of a section drawing is that you can walk into it. The stair the architects drew in profile is the stair you climb; the ceiling heights they dimensioned are the ones over your head. Guided tours of the mansion run year-round — see experiences and tours or plan your visit, and bring the drawing with you in your head.

Keep reading: Can you take photos inside the Pillsbury Club?