The Mother Road, Peer-Reviewed

Elevation at the riverbank: 143 metres. Grade of the approach ramp: negligible, 2 percent, no complaints. Temperature swing since dawn: 6 degrees, mild by the standards of what's coming. The truss bridge that carries the old alignment over the Mississippi is a Warren truss, riveted, not welded, which puts it comfortably pre-1960 and tells you the engineers trusted redundancy over elegance. Every diagonal doubles as a backup for its neighbor, so a single failed member doesn't collapse the span, it just makes the bridge inspector's job easier. I stood on the shoulder for ten minutes counting rivets instead of taking photos, which is either professional deformation or the reason I'm writing this at all.

Grade: B-plus. The original riveting has held for a century of freeze-thaw cycles that would embarrass a lot of concrete built forty years ago. Deducting the half-grade for the resurfaced deck, poured thicker than the original design load ever accounted for, because someone decided smoother ride quality was worth ignoring the dead-load calculation. It isn't going to fail on my visit, and it also isn't going to make the hundred-year mark without someone quietly re-rating it.

I filled the tank in St. Louis for $3.62 a gallon and pointed the car west on the frontage road that still calls itself 66 in defiance of the interstate running parallel forty feet away. Missouri keeps the old alignment stitched together with green shields and gaps where the state simply gave up and told you to merge onto I-44 for eleven miles. I did not enjoy those eleven miles. Nobody does.

Elevation at the summit: 1,128 metres, up from 795 metres at Oatman itself, a gain of 333 metres in fourteen kilometres of switchback. Grade: 15 percent in the tightest curves, unposted, because the road was cut by hand in 1926 by men who did not have a grade study, just a mule train and a mountain that needed crossing. Temperature at the Colorado River crossing that morning: 34°C by nine a.m. Ninety minutes later, at the summit, it read 24°C, a ten-degree drop earned entirely by altitude. My brakes smelled like a hazard report by the time I pulled into Oatman, and that is not an exaggeration for effect, it's a stated fact: sustained braking on a 15 percent grade for fourteen kilometres will overheat pads not rated for it, and two cars pulled over ahead of me for exactly that reason.

Oatman survives on the burros that wander down from the hills their mining-town ancestors left behind, descendants of pack animals turned loose when the mines closed in the 1940s and never rounded back up. They stand in the middle of the two-lane road expecting carrots, and southbound traffic simply stops, which is its own kind of load-bearing structure, an entire local economy resting on the patience of tourists in rental cars.

The storefront sells turquoise jewelry, plush burros, and, per the hand-painted sign, 'scorpions,' which turned out to be real dead scorpions embedded in resin paperweights, $8 each, and not a typo I was hoping for. Its owner told me the building dates to the 1920s mining boom and has 'never needed a single repair.' The door frame disagreed with her, visibly out of plumb by what I'd estimate at two centimetres over its height, which is either settling that stabilized decades ago or settling that hasn't finished yet. I didn't have a level in the car, and I regret that more than most engineering oversights of my career.

Elevation: 0 metres, officially, though the pier itself sits roughly 9 metres above the water on timber pilings driven into the seabed in 1909 and replaced in sections ever since. Grade: the parking ramp down to the beach lot, 11 percent, steeper than anything Missouri bothered building and steeper than most of the mountain I just came down. Temperature: 22°C, marine layer, a ten-degree drop from the desert two hundred kilometres inland that morning, which after three weeks of dashboard thermometers felt less like weather and more like a data point.

The pier's timber substructure is rated, per the placard near the entrance, for pedestrian loads only, no vehicles past the service gate, and the wood underneath has clearly been replaced piecemeal rather than as a full re-deck: newer pale planks alternate with silvered, decades-weathered ones in a pattern that reads less like design and more like a maintenance budget spent one grant at a time. Grade for the pier: B-minus. It's still standing over a century of Pacific swell, which is more than most timber structures manage, but the patchwork repair strategy means nobody has a single clean drawing of what's actually holding the far end up anymore, and I'd bet money the last full inspection report has a line item that says 'assumed adequate' at least once.