On September 3, 1777, the flag of the United States was flown in battle for the first time at Cooch's Bridge, Delaware during Revolutionary War. An excerpt from the article:
"The Battle of Cooch's Bridge was also known as the Battle of Iron Hill. It was between the Continental Army and American militia and primarily German soldiers serving alongside the British Army. It was the only significant military action during the war on the soil of Delaware (though there were also naval engagements off the state's coast).
It took place about a week before the major Battle of Brandywine. Reportedly, the battle that saw the first flying of the U.S. flag.
On August 25, after landing in Maryland as part of a campaign to capture Philadelphia, the seat of the Continental Congress, British and German forces under the overall command of General William Howe began to move north. Their advance was monitored by a light infantry corps of Continental Army and militia forces that had based itself at Cooch's Bridge, near Newark, Delaware.
On September 3, German troops leading the British advance were met by musket fire from the U.S. light infantry in the woods on either side of the road leading toward Cooch's Bridge. Calling up reinforcements, they flushed the Americans out and drove them across the bridge."