Steve Allen laid the foundation in 1954 when he began the Tonight Show & Jack Paar put in the support beams when he took over in 1957. Without them Johnny would never have had his 30 yr showcase.
But, it was Johnny Carson who built the show into an American institution. He created so many memorable characters: Carnac the Magnificent, the (alledged) psychic; Aunt Blabbie: Art Fern & his Tea Time Movies that were more ad than movie. These are the memories I cherish. I could go on & on about the guests, the animals, etc. There are many comedians out there today who owe their start to him.
He started out here in Iowa & as so many have pointed out, he may have left Iowa, but Iowa never left him. That is a huge part of his success.
I could go on & on, but it would just repeat so much that has already been said. Instead listen to Bette Midler's recording of her final appearance on her Greatest Hits album. She sings "One for My Baby" with minor changes. What she sings says it all.