The idea of the New York City apartment as we know it had yet to be established at the end of the 19th century. The inhabitants of huge multi-occupant living spaces were mostly low-income immigrant families, isolated physically and culturally. The change began with Jacob Riis’s 1890 book How the Other Half Lives, which shocked upper and middle class New Yorkers with descriptions and photographs of the abject poverty of the slums. As the 20th century began, improvements to tenement living, changes to laws mandating building height, and the new subway lines paved the way for the apartment to become…