On this day.

[Coog]

On May 10, 1801, the Pasha of Tripoi declared war on the U.S., not through any formal written documents but in the customary Barbary manner of cutting down the flagstaff in front of the U.S. Consulate. Algiers and Tunis did not follow their ally in Tripoli. Yusuf Karamanli, the Pasha (or Bashaw) of Tripoli, had demanded $225,000 from the new Jefferson administration. (In 1800, Federal revenues totaled a little over $10 million.) Putting his long-held beliefs into practice, Jefferson had refused the demand.

In response, "Jefferson sent a small force to the area to protect American ships and citizens against potential aggression, but insisted that he was 'unauthorized by the Constitution, without the sanction of Congress, to go beyond the line of defense.'" He told Congress: "I communicate [to you] all material information on this subject, that in the exercise of this important function confided by the Constitution to the Legislature exclusively their judgment may form itself on a knowledge and consideration of every circumstance of weight." Although Congress never voted on a formal declaration of war, they did authorize the President to instruct the commanders of armed American vessels to seize all vessels and goods of the Pasha of Tripoli "and also to cause to be done all such other acts of precaution or hostility as the state of war will justify."

[csadn]

...and 200+ years later.... :P

[Anav]

Also:

‎1775 - Force under Ethan Allan and Benedict Arnold cross Lake Champlain and capture British fort at Ticonderoga, New York.
1800 - USS Constitution captures Letter of Marque Sandwich.