Au contraire ! You're not going back far enough. Buick was known as an upscale car, a doctor's car, a near Cadillac without the flash.. Unless you want to count the Century as a performance car. The Century was the short wheelbase Special with a Roadmaster engine. But Buick was not known as a performance division at all during the 1950s. The lineup included the Special, the Super, the Century, the Roadmaster and the Limited. They must have been doing something right because Buick during the 1950s was the third best selling marque made in the US.
Well, I own a Buick in the Century vein; the 'short-wheelbase Invicta with the Electra engine' (tho that's changed to a '72 Riviera engine, courtesy of my deranged hands). But yes; the Century was indeed a performance car... up until ChryCo started up with the Hemi. Buick's were seen in competition on numerous levels in this period, and was there when NASCAR / Grand National racing started in '49.
As far as sales go, Buick did well in the first half ['50: 3rd, 4th, 4th, 4th, 4th, 3rd] but slid after that ['56: 3rd, 4th, 5th, 7th]. By '60 they were in 9th place. And perhaps not co-incidentally, Buick's performance leaning got de-emphasized right about at the top of that slide; circa '56. The Special line of '61 started contributing nicely to the volume, but it was a return to emphasizing (limited) performance circa '62/63 that lifted the brand back to 5th by '64; Riviera, Gran Sport models, rejuvenated Wildcat, multi-carbs & 4-spds, etc.
