The Loyalist party was born from the split between American radicals and traditional British rule during the American Revolution. Though many people, such as the Patriots, refused and denounced British rule, many were still faithful as it was still the most powerful nation in the world.
The American Revolution caused many people to choose sides. Unfortunately, Loyalists were at the mercy of the Patriots if left unprotected by the British. The Patriots were a merciless band of American radicals that seized property and brutally attacked anyone that looked like they supported British rule. Many times, the Patriots would tar and feather any Loyalist they found in order to humiliate them and teach them a lesson. As many as one in six Americans were known to be a Loyalist, however historians believe that this number would have been higher if the Patriots acted less rash.
In addition, many black slaves aided the growth of the Loyalist party. Upwards of 50,000 slaves were known to have left their Patriot owners and join the British because they were promised to be free. However, toward the end of the war, when the Americans won, the British only managed to evacuate approximately 20,000 slaves. The slaves' loyalty won them their freedom when they reached Britain. Furthermore, at this point, approximately 80,000 Loyalists left America and joined countries such as Britain and Canada.