Completed in 1884, the Washington Monument was then the tallest stone structure in the world and remains the tallest structure in Washington DC, a limit fixed by law.
The monument tells its own history in its stones. Look carefully at the color change about a third of the way up — a slightly different shade of marble where construction halted in 1854 and didn't resume for twenty-three years. Why the gap? The Know-Nothing Party, a nativist political movement, seized control of the Washington Monument Society in 1855, and the Civil War consumed national attention and funding after that. When construction resumed in 1879, the new marble came from a different quarry, and the color never quite matched.
The cornerstone was laid in 1848, with ceremonies attended by a young congressman from Illinois named Abraham Lincoln. At completion, the obelisk stood five hundred fifty-five feet tall — taller than the Cologne Cathedral, taller than any building on earth.
Before you go up, notice the aluminum apex at the very tip. When the monument was completed, aluminum was more valuable than gold. Only later did electrolytic smelting make aluminum cheap and common. The designers placed the most precious metal they knew at the very top, and within a decade it was worth almost nothing.
From the observation level on a clear day, you can see Maryland and Virginia in every direction. L'Enfant designed the city to radiate from this approximate spot.