In the 1920’s hundreds of Americans died every year in tornadoes. Tornado deaths are much less common now, despite the fact that the number of people in harms way in Tornado Alley is much larger.
US Annual Tornado Death Tolls, 1875-present – NOAA Weather Partners
It may be some trade off between better warnings and better construction vs. far greater population. Although the better construction part I am not so sure about given all the people living in trailers and other low budget shelters. I don’t know enough about that aspect of the subject to comment intelligently. Maybe someone else can.