Business Affected With A Public Interest

What does Business Affected With A Public Interest mean in American Law?

The definition of Business Affected With A Public Interest in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

A phrase used in early (nineteenth century) Supreme Court cases upholding state regulation of business activities beyond the scope then thought generally proper. While no definition was ever successfully promulgated, certain touchstones developed, e.g., the market power of the enterprise (e.g., the only grain elevator in a locality); the closeness of its connection with necessities of life and health (e.g., milk production and marketing); and especially combinations of those two factors (railroads; utilities).

The more recent (post-1930″s) ubiquity of state and federal regulation of business activities has made the concept unimportant, indeed almost quaint. Cf public utility.