The club started to grow "with splendour" despite the severe effects of the Spanish–American War, followed by brief economic prosperity resulting from Spain's neutrality during World War I. In 1919, Alba wrote a letter to Colt expressing the unprecedented expansion that the club was going through. The three hundred members of 1913 had more than doubled. Reforms had to be made to increase the club house in size and the entry fee for new members raised. Puerta de Hierro introduced a "pay for use" policy whereby members had an extra fee for each sport they desired to play; 180 pesetas for those wishing to use the golf and tennis facilities and 350 for polo. Foreigners paid 50 pesetas monthly, but were exempt from any entry fee.
