By 1875, the Congressional Library in the Capitol Building had outgrown its shelf space, forcing librarians to store incoming books, maps, music, photographs, and documents in stacks on the Library floor. Eventually, Congress approved a plan to move its Library into a new structure that would be built across from the Capitol, and by the end of the summer of 1897, all 800,000 books had been moved into the newly opened Library of Congress building, known today as the Jefferson Building. While the books now had plenty of space, a new challenge presented itself: how would the congressmen have easy access to their library if it was now a quarter of a mile away? The solution was a technological creation that seems futuristic at the very least: a special underground tunnel full of conveyor belts and pneumatic tubes that connected the two buildings, and had books zooming to and fro under First Street SE for nearly the next century.