If you consider Brittany as being Cetic, which it is, then it was backward in comparison with the rest of France well until th 70s or so, probably even later, and was considered as backward (with its specific culture and or at technical level) by the rest of the country, as if their was France on one side and Brittany on the other. You could lmost say that for everything in France you could trace a line, and Brittany was always on the downside. But nowadays the place do pretty well : one of the first place for tourism, pretty good in agricol activity, some hightech entreprises being placed there (mostly at Rennes and Nantes, if you consider Nantes as being part of Brittany. By the admnistrative division it isn't, but hey), there's also important military bases such as Brest, which contain the SNLE, the french nuclear-powered and -missile launcher submarine (And given the location would still be there unless a POD prior to the mid-17th century). But it could I think easily remain backwrd given a god POD.
Don't know about Galicia (the Spanish one). It is sometimes considered as Celtic, and is part of the Celtic nation, but I don't know if it is backward in comarison with Western European standard as a whole, or even with spanish standard.