The Washington Monument is constructed primarily from three distinct types of stone, which is why you can see a visible change in color about one-third of the way up the structure. The exterior is composed of Texas marble (from Maryland), Sheffield marble (also from Maryland), and Lee marble from Massachusetts. The first phase of construction used marble from a quarry in Texas, Maryland, but work was halted for 25 years due to a lack of funds and the American Civil War. When construction resumed in 1879, the original quarry was no longer available, forcing the builders to source stone first from Massachusetts and then from a different quarry in Maryland. While the builders tried to match the original white marble, the different mineral compositions caused the stones to weather differently over time, resulting in the "two-tone" appearance we see today. The interior of the monument is lined with Maine granite, and the walls are inset with 193 commemorative stones donated by various states, cities, and foreign nations, made from materials ranging from jade and copper to native sandstone. This massive obelisk stands as a geological patchwork, reflecting the long and fractured history of its own creation.