Orsières is where the Valais valleys split apart. Here the road from Martigny forks: one branch climbs into the Val Ferret toward Champex and the Mont Blanc massif, the other follows the Val d'Entremont up toward the Great St Bernard. The town has a little under three thousand inhabitants, the Dranse river rushing through it, and a small narrow-gauge railway that comes up from Martigny and ends at the station. It is the last real place of any size before the pass, and so everyone who rides the road stops at some point.
That makes it the right place to fill up. Fuel is here, along with supermarkets, bakeries and cafés, and there is no reliable supply for a long way after. The next pumps higher up are scarce, so take the opportunity. The valley road runs from here through Liddes and Bourg-Saint-Pierre, with the climb steadily increasing, and the last section above the tree line is a lot less forgiving than the lower valley.
The road itself has been an artery for two thousand years. The Romans used the pass, calling it the Summus Poeninus, and built a temple on the summit. Charlemagne's armies came this way, as did countless pilgrims heading to Rome, and Napoleon marched his army across in 1800 on his way to Italy, an event so famous that the hospice at the top still sells postcards of it. The hospice, run by Augustinian canons, has looked after travellers for nearly a millennium, and its dogs became world famous.
Today a long tunnel under the mountain carries the heavy traffic, which leaves the pass road quiet in good weather and gloriously empty in the shoulder seasons. Keep in mind that the pass is closed by snow for much of the year, normally from autumn until early summer, while the tunnel stays open for a toll. In good weather the climb from Orsières is a joy: smooth, broad curves in the valley, then a sequence of hairpins above Bourg-Saint-Pierre, with the Combin glaciers visible away to the east.
If you arrive in the evening, linger a while over a meal. The Valais kitchen offers dried meat, raclette made with local cheese and the white wines of the lower valley, and it all tastes better after a long day in the saddle. Mountain weather turns fast, so check conditions before the climb.