Route Royale (Royal Road), Route du Sel (Salt Road)

The road you are on is called “Route Royale” (Royal Road) or “Route du Sel” (Salt Road), which once linked Saint-Claude to Geneva via Mijoux and Gex. At the time, the Jura would sell salt from Lons-le-Saunier to Switzerland. The road was built in 1742 by “corvées”: taxes paid in days of work.
The narrow “Route Royale” was deemed too dangerous due to its short steep bends and was replaced during the early 20th century by the current road between Lajoux and the La Faucille pass.