1. The Old Canal Lockkeeper’s House was built along the Washington City Canal, which ran through the Mall in the 1800s and linked to the Chesapeake and Ohio Canal. President Washington hoped the District would be a major port, but it was not to be. The city canal was filled in in the 1870s.
2. Political squabbling halted construction of the Washington Monument in 1858. For decades, it was merely a stump.
3. Construction on the Smithsonian Castle began in 1847, a year after the Smithsonian Institution was established.
4. The imposing, red-brick Army Medical Museum and Library building stood here from the 1880s until 1969, when it was razed to make way for the Hirshhorn Museum and Sculpture Garden.