The U.S. brig that became Oliver Hazard Perry's flagship after USS Lawrence was disabled at Lake Erie was USS Niagara.
The transfer occurred during the Battle of Lake Erie on September 10, 1813. Perry's original flagship, Lawrence, had been battered by British fire, losing most of its effective fighting capacity and suffering extremely heavy casualties. Perry lowered his battle flag and crossed by boat to the still-operational Niagara.
From Niagara, Perry reorganized his squadron and broke through the British line. The American victory secured control of Lake Erie and helped General William Henry Harrison recover Detroit and advance into Upper Canada. Perry later reported, “We have met the enemy and they are ours.”
A common mix-up is that Lawrence remained Perry's flagship throughout the entire battle. It was his initial flagship; Niagara became the active command ship after the transfer. The two brigs were sister ships built for the American Lake Erie squadron.