middle-class families women took control of the purchasing, and the department stores catered to their tastes. Furthermore, ambitious young women from the middle class who wanted a career were welcomed into the clerical ranks, where they developed social skills to work with their upscale customers.Susan Benson, Counter cultures: Saleswomen, managers, and customers in American department stores, 1890-1940 (1987). Skyscrapers and apartment buildings New inventions facilitated the emergence of the skyscraper in the 1880s—it was a characteristic American style that was not widely copied around the world until the late 20th century. Construction required several major innovations, including the elevator and structural steel. The steel skeleton, developed in the 1880s, replaced the heavy brick walls that were limited to 15 or so stories in height. The skyscraper also required a complex internal structure to solve issues of ventilation, steam heat, gas lighting (and later electricity), and plumbing. The city's housing involved a wide variety of styles, but most of the attention focused on the tenement house for the working class and the apartment building for the middle class. The apartment building came first, as middle-class professionals, businessmen, and white-collar workers realized they did not need and could scarcely afford single-family dwellings in the high-cost real estate districts of the city. Boarding houses were inappropriate for family; hotel suites were too expensive. In outlying neighborhoods there were many apartments over stores and shops, usually occupied by proprietors of small local businesses. Apartment dwellers paid rent and did not own their apartments until the emergence of cooperatives in the 20th century. Turnover was very high, and there was seldom was a sense of neighborhood community.Elizabeth Collins Cromley, Alone Together: A History of New York's Early Apartments (1990) Starting with the luxurious Stuyvesant Apartments that opened in 1869, and the even more lavish The Dakota in 1884, affluent tenants hired full-time staff to handle the upkeep and maintenance, as well as security.Andrew Alpern, New York's Fabulous Luxury Apartments: With Original Floor Plans from the Dakota, River House, Olympic Tower and Other Great Buildings (1987) covers 75 famous buildings starting in 1869. The less-lavish middle-class apartment buildings provided gas lighting, elevators, good plumbing, central heating, and maintenance men on call. Apartment buildings were built along the paths of the street railways since the middle-class tenants rode the streetcar to work, while the working class saved a nickel each way and walked. The working class crowded