It is natural to assume that America’s landmarks have always been a part of our national fabric. It’s hard to imagine the National Mall without the Washington Monument or Mount Rushmore without, well, Mount Rushmore. But a look back into the archives at the Library of Congress shows the “in progress” stages of some of the nation’s most treasured sites. Whether it’s a scaffolding hanging off the White House or two hunks of steel in place of the St. Louis Arch, these photographs paint a picture of a country in the process of making its own history.