Mayor Vince Gray showed what a history buff is this morning by tweeting out an important anniversary — it was on this day in 1791 that the young capital city was named, with the federal district being referred to as the “Territory of Columbia” and the federal city taking on the title of the “City of Washington.” (This is what it probably looked like.) It wasn’t until 1871, when the city was formally incorporated, that “District” replaced “Territory,” giving birth to what we now know as Washington, D.C.

UPDATE: DCRA spokesperson Helder Gil kindly fills us in on what is going on with those lots that are stretching into the Anacostia River. “The mystery lots on far right were built when part of Anacostia River was filled in,” Gil tweeted.