It was in 1974. And it was a mere 2nd category climb. Yep.valentius borealis said:With regards to French climbs, don't forget that Le Mont du Chat has been used once in Le Tour.
At the time, the Hors Catégorie ranking didn't exist and the 1st category was only for the great and high climbs like Galibier, Tourmalet, Izoard... Mont du Chat was "only" 1500 meters high and they didn't had an emphasis on the "climb statistics" like the gradient. Length, altitude and "prestige" were the only way to classify climbs back in the day. If the Mont du Chat made its comeback it would be undoubtedly be rated HC whatever the side (the profile here is the west side with the final 8 km @ 10.9 % - the east side is 13.4 km @ 9.3 %).
Also climbs like Pra Loup (1980) or La Ruchère (1984) were rated HC. By today's standards, Pra Loup would be 2C and La Ruchère 1C.
The col du Granon, climbed in 1986, is also very hard (11.5 km @ 9.05 % - 2404m high), albeit a bit short. But the altitude is what makes this climb hard.