Chain stores became an important force in the American economy around the turn of the century. Mass production (and the accompanying potential for mass consumption) made this new business model possible. Innovators saw that they could make more money from high-volume low-margin sales than from the low-volume high-margin sales that characterized traditional retailers, who were accustomed to a slower pace of business.
High-volume sales strategies were first perfected by urban department stores (Macy's, Marshall Field) and by the famous Sears catalogue (which catered to rural customers) in the mid-late 19th century. The department stores demonstrated the potential of business models focused on lowering costs/prices through centralized management and purchasing in bulk while focusing on increasing the "velocity of flow" of products through the shops ("stock-turn"). Alfred Chandler called this model an "economy of speed."
Starting in the 1880s, chain retailers such as Woolworth and Atlantic & Pacific borrowed the department stores' business models, but also used modern management techniques to build more flexible organizations that could cover wider territory:
The chains had to administer a number of geographically scattered
united. Nearly all the larger chains acquired regional managers with a
staff of accountants and "inspectors" or "road men" who kept a
constant check on the sales and financial performance of the managers
of the individual stores in their own territories. For all these
middle managers stock-turn remained the basic criterion for success. (p. 235)
Chains soon became more important than department stores or mail-order catalogues, causing these businesses to imitate the chain store in the 20s and 30s:
Because they covered a broader and faster growing market than did
either of the other two types of mass retailers, the chains began in
the twentieth century to grow more rapidly in number and in volume of
sales than did either the mail-order house or the department store.
The chains were better suited to respond to the changes in consumer
buying resulting from the increased mobility made possible by the
coming of the automobile and from the rapid growth of the suburbs.
Faced with a declining rural market in the 1920s, the two great
mail-order houses--Sears Roebuck and Montgomery Ward--organized chains
of several hundred retail stores between 1925 and the coming of the
great depression in 1929 . . . By the 1930s, department stores . . .
had begun to build branches in the suburbs of the cities they served. (p. 235)
TL;DR from Chandler himself:
The chains with their geographically widespread network of branches
completed the retailing revolution begun by the department stores in
the 1860s and 1870s. They did so because they created administrative
organizations that coordinated a higher volume flow of goods from the
manufacturer to the largest number of final consumers in an
increasingly urban and suburban community. (235)
Source: Alfred Chandler. 1977. "The Visible Hand: The Managerial Revolution in American Business."