<human>:  When did the battle of Lexington take place?
<bot>: The Battle of Lexington took place on April 19, 1775. It was the first major battle of the American Revolutionary War. The battle occurred in Lexington, Massachusetts, and was fought between British troops and the local militia. The British troops were led by General Thomas Gage, who was the British military governor of Massachusetts. The American militia was led by Colonel John Parker, who was a veteran of the French and Indian War.