The Portsmouth division of the Royal Marines was located at Eastney Barracks, which opened in 1864 to house the whole of the Royal Marines Artillery (RMA) Division. The subsequent development within the Barracks reflects the changes in the role of the Royal Marines throughout the 20th century - from the move to an amalgamated Royal Marines Barracks in 1923, to the final departure of RM Commando Training and Reserve HQ in 1991. The population of the Barracks would also vary according to war or peace status - as a RM Artillery division, around 2000 men could be present, while by 1990 there were barely 40 Royal Marines located there.
In 1973 the Royal Marine Museum was opened in what was the Officers Mess of the Royal Marine Artillery up until 1923. In the area surrounding the museum can be seen the rest of the Royal Marines barracks, Eastney which have since been redeveloped for private housing.