I’ve seen it written that kettlebells were completely unknown in the US until the late 90’s but that’s not exactly true… I wouldn’t say that they were tremendously popular, but people have certainly known about kettlebells on these shores and trained with them for many years prior. Sig Klein was always big fan of kettlebells and discussed them often in his articles and courses. To give you one example, this article, “Kettlebells for ‘Different’ Development” appeared in Strength and Health magazine in the late 1950’s.