Spider-Man showed up on the Electric Company in 1974, when I was ten years old. I was already a dedicated PBS viewer when the show appeared a few years earlier, and a live action Spider-Man, even if he was in rather corny shorts like above and never spoke, was a must watch.
There was also an Electric Company magazine that I was a big fan of too. I remember it have single-page origin stories for Marvel superheroes for a year or so. Heady stuff for ten-year-old.
And yes, that is Morgan Freeman.