What year did Kermit leave the swamp?

When Mr. Wilson grabbed the two frogs in the road as Kermit and his pal looked on, he got back in his truck and turned on the radio. BTO's "Roll On Down The Highway" could be heard as he headed to his pet store. That song came out in 1974, which is curious because Kermit could be seen in episodes of Sam and Friends in 1955. I suppose it's possible that he still lived at home and the show was taped in the swamp area (I never saw that show). However, by 1969 Kermit hit it big with Sesame Street. Obviously, he didn't still live in a swamp at that point because the show's location was a street and in Kermit's Swamp Years he is shown seeing a road for the very first time in his life.

I'm a real kewl kat.🐈