1789: The states ratify the U.S. Constitution, which says, in relevant part, that “No Person shall be a Representative who shall not have attained to the Age of twenty five Years.”
1797: William C.C. Claiborne is seated as a Representative from Tennessee, at age 22.
I’d love to know more about whether any constitutional objections were raised to this; Joseph T. Hatfield, William Claiborne: Jeffersonian Centurion in the American Southwest (1976), doesn’t discuss any controversy about this, and a research assistant whom I asked to look through the Knoxville Gazette for 1796 to 1798 didn’t find any articles mentioning any controversy about this.
Henry Clay was sworn in as U.S. Senator on Dec. 29, 1806, when he was three and a half months short of the constitutionally required age of thirty. I couldn’t find any evidence that there was any controversy about that, either. On the other hand, Albert Gallatin was denied a Senate seat in 1793 on the grounds that he hadn’t satisfied the constitutional requirement of having “been nine Years a Citizen of the United States.”
Some time later, the houses of Congress apparently started to focus more on such issues. (See also this item, which indicates that by 1860 the age requirement was being more carefully attended to.) But it seems surprising that in the early years, no objections were apparently raised. If any of you know more of the reasons why such obviously unconstitutional actions didn’t seem to raise an eyebrow — Was the provision thought to be hortatory? Was popular sovereignty as to Representatives, or state authority as to Senators, thought to be a higher law, at least when it came to age rather than citizenship? — or know whether eyebrows were actually raised, I’d love to hear it. (Note that I don’t think there was any doubt or uncertainty at the time about Clay’s or Claiborne’s age, and my sense from the biography of Claiborne is that Claiborne’s youth was well known.)