The logo for Kirk Miller's debonair menswear label, Miller's Oath, is a pickax. Although this might seem suspiciously of-the-moment, given the number of designers currently mining Americana heritage, for the 33-year-old Minnesota native, the frontier-meets-luxe look is a natural fit. Around the turn of the 19th century, his great-grandfather owned a dry-goods store in Groton, South Dakota, where he and his eight brothers sold things like chicken feed and hand tools and, for $5 apiece, cashmere suits. The suits weren't for lounging. "All this clothing...stuff was meant to be done in it," Miller says. "Farmers wore a jacket and pants."

At the designer's shop in lower Manhattan, a pearl-gray dinner jacket with grosgrain lapels is draped snugly over a rumpled silk vest and a wing-collar shirt made of beefy cotton piqué. Should you enlist Miller, for $3,000 and upward, he will make you one of his very sharp bespoke suits, which take up to eight weeks and three fittings. You will get to know the store well: the buffalo-hide carpet; a stiff pair of black riding boots by the door; and some beautiful casual clothes, such as cherry-red corduroys and navy cardigans, folded on top of a weathered picnic table.

Surrounded by a few well-edited and suggestive elements, Miller—blond and blue-eyed, and boyishly handsome—sits smack in the center of the store at a simple table. (He prefers to handle sales himself, and when he must be out of town, he calls his father to step in.) Walk into the store in the early-morning hours and chances are Miller will be there, sipping a coffee and poring over books of fabric suiting.

He loves tweed, he says, as he thoughtfully runs his fingers over various swatches. Miller handles a robust, tightly woven Scottish tweed that might make a perfect riding coat, then a refined and clubby English tweed, followed by a loosely constructed Irish tweed. "You can almost see the guy coming out of the pub with his newspaper stuffed in his jacket, can't you?" he asks.

Some nouveau tailors will have you settle into an armchair and sip single malt, as if you were Lord So-and-So, awaiting a new batch of smoking jackets. Miller isn't one of them. "I kind of loathe those custom shops that want you to hang out," he says. "I mean, I want it to feel inviting, but most of my guys aren't coming here to sit on the couch and talk and drink whiskey. They're here for a purpose."