In my memory as a boy, Louis Armstrong was this big-smiling, gravel-voiced musician on the radio - that big console that sat in our living room, more often doing Bing or Sinatra - and (once our family finally got a television!) turning up on TV variety shows all the time. He obviously was loved and respected by all. I really didn't know why. He was cool, but not as cool as Elvis.
Of course, young boys, by definition, lack a certain historical perspective. I recently learned, for instance, that it was Armstrong who first used the word "chops" to admire a musicians' ability. He was the first to call anybody a "cat." And he spent essentially two years on the run after refusing to bow to the demand from New York night club owner and big-time gangster Dutch Shultz to show up at Shultz's establishment. A command performance, so to speak. At the time, a time of illegal liquor and machine guns transported in violin cases, that took some guts.
Of course, (and I have to take others' word for this), Armstrong is most famous for changing American singing. The early 20th Century world of ragtime and the Charleston suddenly had to deal with scat and other innovations that I can hear, but don't have the smarts to describe.
Still, for that youngster that was me, there was something life-changing about just seeing Armstrong, Lena Horn, and other black performers on the tube. They were better, I think I understood in my limited, childlike way, than any of their white contemporaries. Louis Armstrong, back in the 1950s, may not have been in my eyes as cool as Elvis (who of course was doing "Negro" music, which pissed off parents more than his pelvic movements), but Louis Armstrong and his fellow artists of that time (Duke Ellington, etc.) were cool enough. Cool enough to help initiate the changes soon to come.