After the Civil War, during which the grounds of the stubby Washington Monument were used as a cattle yard and slaughterhouse, Congress finally decided to take over. On July 5, 1876, in time for the centennial celebration of the Declaration of Independence, Congress appropriated $2 million for the completion of the monument and construction resumed in 1877.
The first task of the new chief engineer, Thomas L. Casey, was to reduce the total height of the obelisk to 555 feet (169 meters), exactly 10 times the width of the structure, and to spend years reinforcing the foundation with concrete.
The next issue was the masonry. The original quarry in Baltimore had shut down, so Casey tried shipping down rock from Massachusetts. But after placing only a few layers of this stone, it was clear that it was a different color and of poorer quality than the original. So, the builders changed tack yet again and brought in stone from another Baltimore quarry, which was used to finish the final two-thirds of the obelisk.
The result is that the Washington Monument is nearly white on the bottom, a tannish-pink on the top with a thin belt of light brown in the middle. Classy, Casey.