Castle William is a British fortification located on a small island in Boston Harbor. Its strategic importance—guarding the harbor and mainland against foreign invasion—shifts to providing a refuge for British troops during the colonial rebellion. Gage uses it as a temporary headquarters, and loyalists (including Hutchinson), fearing for their lives, retreat to the island for protection until hostilities cease or they can secure safe passage back to England.

When Washington’s troops surround Boston and fire upon the city, Howe moves most of his forces to Castle William to regroup for a counterassault, although bad weather prevents a safe landing on the shore. Castle William, the oldest fortification in the United States, is a vital cog in the British defenses, an ideal tactical location for repelling an assault by sea against one of the most populous colonies.

Although John Adams bemoans the glacial pace of the Continental Congress—its endless debates and speeches that yield very little tangible results—the congress is a monumental step in the path toward American independence. For the first time, the colonies unite as a single representative body, putting their cultural differences aside to address the problem of British rule. The congress is significant also as a statement to England that the colonies can unite.