The primary reason the colonists fortified Bunker Hill was to gain control of Boston.

By seizing this elevated terrain, the colonial forces sought to limit British access to the city and its harbor, both of which were essential for British military endeavors. The fortifications held considerable strategic importance, enabling the colonists to challenge British positions in Boston and demonstrate their involvement in the conflict. This action illustrated the increasing resolve of the colonists to oppose British rule and secure a presence in the intensifying fight for independence. In the end, the fortification of Bunker Hill was crucial in the subsequent battle.