In the 1850s a new industry emerged when refiners discovered that refined petroleum (which up until that point had been bought chiefly for its supposed medicinal properties) made an ideal fuel for lamps. (It would not become important for fueling engines until the twentieth century.) Production boomed; wells sprang up as large oil fields were discovered in Pennsylvania and the Midwest; and hundreds of small firms sprouted. In the decades after the Civil War this buzzing, frenetic activity formed the backdrop for the emergence of a new way of organizing business on an unprecedented large scale: the business trust. The instrument that devised this innovation was the Standard Oil Company, led by John D. Rockefeller.

Growth.

Rockefeller had amassed effective control over oil refining in Cleveland in the late 1860s and early 1870s (Cleveland being an important refining region) by promising railroads a...