Massachusetts Hall was completed in 1720 and is the oldest surviving building in Harvard Yard. Built to provide student chambers, it belonged to a small colonial college whose campus consisted of only a handful of structures. Harvard trained ministers, lawyers, physicians, and public officials, many of whom entered the imperial controversies that preceded independence. The hall's ordinary academic purpose changed abruptly after fighting began at Lexington and Concord on April 19, 1775.

Cambridge became the headquarters and principal camp of the New England army gathering around British-held Boston. Thousands of militia arrived faster than commanders could provide shelter, food, sanitation, or organization. Massachusetts authorities closed Harvard and moved students and instruction temporarily to Concord. The college's buildings were then requisitioned for military use, turning dormitories and classrooms into quarters for soldiers participating in the siege.

Massachusetts Hall housed approximately 640 troops during 1775 and 1776. Men slept and stored equipment in spaces designed for students, while neighboring Harvard, Hollis, and Stoughton halls and Holden Chapel also supported the army. The concentration strained buildings and grounds. Military occupation brought dirt, wear, disease concerns, and repair costs, but the campus's location near headquarters and fortifications made it an obvious resource for a force that had few purpose-built barracks.

When George Washington arrived in July 1775 to command the newly created Continental Army, Cambridge became the administrative center of the siege. From this area officers imposed greater discipline, organized regiments, gathered supplies, and maintained pressure on Boston. The army eventually used Henry Knox's artillery to fortify Dorchester Heights in March 1776, compelling the British evacuation. As the military emergency eased, Harvard returned from its temporary exile and reclaimed its buildings.

Massachusetts Hall resumed academic use and underwent repeated interior alterations over the next three centuries. Today its lower floors contain university offices and its upper floors remain student rooms. The exterior and substantial historic fabric survive, but the modern interior is not a preserved 1775 barracks. Its continued use distinguishes the building from ruins or reconstructed military sites and demonstrates how an institution can adapt a historic structure without freezing it in one period.

The building's Revolutionary significance lies in conversion rather than combat. It shows how civilian institutions supported the improvised army surrounding Boston and how war disrupted education, housing, and ordinary routines. Students left so soldiers could occupy their rooms; a college campus became military infrastructure; then the same walls returned to scholarship. The marker allows visitors in Harvard Yard to connect national events with that practical transformation and to recognize the surviving hall as a witness to the earliest organization of the Continental Army.