The building of the monument proceeded quickly after Congress had provided sufficient funding. In four years, it was completed, with the 100-ounce (2.83 kg) aluminum apex/lightning-rod being put in place on December 6, 1884. The apex was the largest single piece of aluminum cast at the time, when aluminum commanded a price comparable to silver. Two years later, the Hall–Héroult process made aluminum easier to produce and the price of aluminum plummeted, though it should have provided a lustrous, non-rusting apex. The monument opened to the public on October 9, 1888."Washington Monument" . Teaching with Historic Places. National Park Service. Retrieved October 15, 2006.
the building of the monument proceeded quickly after congress had provided sufficient funding in four years it was completed with the 100-ounce (283 kg) aluminum apex/lightning-rod being put in place on december 6 1884 the apex was the largest single piece of aluminum cast at the time when aluminum commanded a price comparable to silver two years later the hall–héroult process made aluminum easier to produce and the price of aluminum plummeted though it should have provided a lustrous non-rusting apex the monument opened to the public on october 9 1888"washington monument"  teaching with historic places national park service retrieved october 15 2006