Final answer:
Prior to the American Revolution, the Old State House in Boston served as the seat of the British colonial government of Massachusetts, hosting the Royal Governor and the Assembly.
Step-by-step explanation:
The purpose of the Old State House in Boston before the American Revolution was C. It housed the British colonial government of Massachusetts. This building served as a focal point for politics and business, and it was where the Royal Governor of Massachusetts and the Massachusetts Assembly conducted much of the colony's business.
The Old State House was also a center of protest against British policies, including the Stamp Act and Townshend Acts, and it witnessed pivotal events leading up to the Revolution, such as the Boston Massacre in 1770.