The gigantic obelisk (in fact the tallest obelisk and the tallest stone structure in the world) commemorates George Washington – the first president of the USA. The Washington Monument is not only an icon of the city but also one of the most iconic landmarks of the whole country.
Its cornerstone was laid in 1848 and it was opened in 1889. There are 896 steps leading to the top of the monument. They are not usually open to the public due to the safety concerns.
Unfortunately, the monument is closed until spring 2019 due to the renovations of the elevator. You can get here by subway, Smithsonian Station (blue, orange and silver lines).
At the moment, the Washington Monument is closed due to the elevator modernisation. It will stay closed till spring 2019. Check the website for further information.