Why yes, they were, in the classical sense. What would they be today? You guessed it! If you disagree, please post quotes from the Founders to support your position.
You have to go further and state that the founders also did not believe in political parties (factions they called them). Individuals make better decisions en mass than a group of motivated people around a single subject. For those of you not living in or around KCMO, they passed a tax and resolution to build an idiotic two mile long light rail system. They waited until the middle of nothing and got about 7% voter turn out. Guess what? All those people wanted someone else to pay for the light rail system including a lot of people who couldn't vote in the election.
Also bear in mind it was a different world and some things would be different. The protection of the ocean is not so absolute as it was 230 years ago. Washington warned against foreign entanglements because, frankly, the US was not ready for it. We needed to build a country first. Jefferson believed the same but started building a fleet to deal with the Barbary Pirates in Africa. He realized that we would have to be in a position to protect ourselves.
For some people here, a liberal today is not the liberal of the founders. A conservative is closer to a classic liberal and, yes, a true libertarian is more of a classic liberal than a conservative. My experience is that many people who call themselves libertarians just want to get away with stuff.
Some "libertarians" are only in the sense of what they want to do. When it comes to someone else doing something then they are libertarians in name only.