Complex sentence: Among those who responded were the volunteers of the Massachusetts 54th Regiment; their contributions are commemorated by an impressive monument, depicting their farewell march down Beacon Street, at the edge of Boston Common, across Beacon Street from the Massachusetts State House.
Split into simpler sentences: Among those who responded were the volunteers of the Massachusetts 54th Regiment. Their contributions were commemorated by an impressive monument, depicting their farewell march down Beacon Street, at the edge of Boston Common, across Beacon Street from the Massachusetts State House.