It's not really true. Before the establishment of the United States as a political entity under the Constitution, there was a body called the Continental Congress that existed in the 1770s and 1780s. The presiding officer of that body was called the President of the Continental Congress, and some people mistakenly think that was the same office as the President of the United States. It wasn't; despite the similar names they were entirely unrelated to each other. I think there were a dozen presidents of the Congress or so, but none of them were presidents of the United States.