I do not know the first time I ever traveled - I have been exceptionally privileged like that. I do know however that as a kid I regularly traveled from where I grew up in central Vermont to Florida to visit my grandmother as well as to Cape Cod to visit my grandfather.
I also grew up about a two hour drive from the Canadian border in an age when passports were not required to cross it by land, so that was likely the first time I left my home country.
There were childhood trips to the beaches of Maine and also regular excursions to the Caribbean. I have a memory of a story of getting into the back of a stranger's truck with my parents and brothers (one of whom must have been under five years old) to get from where a boat dropped us off on an island to the little bar my parents wanted to go to.
The first trip though, that I can really distinctly remember was to England, Belgium, and France the summer I turned 12. My birthday is Bastille Day and the year we spent it in Paris.
Later, in high school, I went to Italy on a 'school program' which basically just meant there were chaperones to yell at us when we kissed Italian boys in the Piazza della Signoria.