In 1763, France, Britain, and Spain signed the Treaty of Paris to end the French and Indian War. As part of the treaty, France gave up almost all of its land in North America and Spain gave up Florida. During the French and Indian War, Britain had captured Havana, Spain's busiest port. In exchange for Havana, the Spanish traded Florida to Britain.
The section of the Jeffreys map of Florida from 1775 right before the American Revolution shows the Charlotte Harbor area at the time the British owned Florida. It was right before the Revolution that the British ( Bernard Romans, the map maker) who gave our harbor its name "Charlotte Harbor" renamed from Carlos Bay. Charlotte was the name of the Queen at the time, George the Third's wife.
The British did not rule Florida for long. The colonies north of Florida began a war known as the American Revolution. Most of the war took place far north of Florida, and Florida sided with the British suffering occasional raids. In 1779, Spain took advantage of Britain's preoccupation with the colonies and invaded West Florida. By 1781, Britain lost West Florida to Spain. And by the end of the Revolution, Spain had regained the rest of Florida.