Slate Alley, which was where the Warner Theatre is today, was home to a few dozen small houses that belonged to tradesmen. Alley dwellers were usually the poorest of city residents who rented tiny houses built by landowners at the rear of their property. At one time, 3,000 of the dwellings existed in the city. Those who lived in Slate Alley were considered part of the "hidden city" because neither their existence nor their houses were officially acknowledged by the District until about 1860. Census takers, and others, were not eager to visit the alleys, which had a reputation for being unsanitary places that bred disease as well as crime. Slate Alley, named for a slate yard that operated in the alley in the 1850s, has disappeared into a vast excavation hole.