Designed in 1818 by Benjamin Latrobe for naval hero Stephen Decatur and his wife Susan, this brick building holds the honor of being the first and last house on Lafayette Sq to be occupied as a private residence. It's also one of the few urban residences in the US retaining slave quarters (in this case built in 1836). The White House Historical Association runs one-hour free guided tours of the house at 11am, 12:30pm and 2pm on Mondays.