Head to the southwest corner of Wisconsin and you'll spot it before you spot much else: a huge white 'M' stamped across the side of Platte Mound, four miles northeast of the small city of Platteville. At 241 feet tall and 214 feet wide, it holds the title of the world's largest 'M' — and it's been staring out over the rolling farmland since 1937.

The letter honours the region's lead and zinc mining heritage, but its origin story is pure student rivalry. In 1924, the engineering club at what was then the Platteville mining school wanted to match the Colorado School of Mines, which had carved its own 'M' on Mount Zion near its campus. That challenge sat dormant for over a decade until the winter of 1936, when two students, Pat Medley and Alvin Knoerr, stomped a giant 'M' into the snow on the mound. It stayed visible for weeks, locals loved it, and by 1937 the university had secured the landowner's blessing and 400 tons of limestone to make the letter permanent. Periodic coats of whitewash and cement have kept it glowing ever since.

The 'M' has had a surprisingly busy media career. Life magazine photographed it in 1949. In 1987, some 650 students arranged themselves on the mound to form the MTV logo for the camera. And in a bid that speaks to Platteville's flair for large-scale human art projects, the city won the right to host Disney's Mickey's Hometown Parade on July 4, 1998 — the only US city ever to do so — after the local Jaycees dressed about 250 volunteers in black and positioned them as Mickey Mouse ears next to the 'M'.

Visiting is easy and free. There's parking at the base of the mound, and the letter faces south at a 45-degree angle, so it photographs well in good light. If your legs are up for it, more than 200 stairs climb to the top of the mound for views across the Driftless Area's unglaciated hills. Better still, pair the climb with a stop at the local mining museum, where you can tour a real lead and zinc mine and understand exactly what the 'M' is celebrating.

For road-trippers crossing the Midwest, this is the kind of detour that costs nothing and makes for a great story back home. It's a quick hop from Platteville's modest downtown, and the surrounding Grant County back roads are pleasant driving country. Just don't expect a gift shop — the appeal here is entirely the scale of the thing, plus the charmingly petty college rivalry that put it on the map. Student one-upmanship rarely ages this well.

Story credit: Atlas Obscura.