Since colonial times, self-employed lawyers, doctors, merchants, and proprietors had been the backbone of a robust American middle class. While independent careers remained important, industrialism spawned a new middle class of salaried employees. Corporate organizations required managers, accountants, and clerks. Industrial technology called for engineers, chemists, and designers, while the distribution system needed salesmen, advertising executives, and store managers. These salaried ranks increased sevenfold between 1870 and 1910 — much faster than any other occupational group. Nearly nine million people held white-collar jobs in 1910, more than one-fourth of all employed Americans