While aluminum is the third most abundand element in the Earth's crust, it is not easy to get the pure metal. The method for extracting aluminum from ore is electrolysis and it relies on a tremendous amount of electrical power. Since electricity in large quantities only became commercially available around the middle of the 20th century, this was the first time in history that enough power was available to economically extract aluminum metal from ore in large quantities. For more details check out the chemical of the week.