For a country accustomed to counting its resources in millions, or even billions, the unit of measure is almost too small to be of interest. But during a lunch break one day, Robert E. Hardwicke asked of his colleagues in the Petroleum Administration for War why American oil is measured by the 42-gallon barrel and no other. Why not 30, 36, or an even 50? No one present had the answer, but a dozen years later, and after extensive research, Hardwicke produced the answer for himself and all others in and out of the oil industry. This book is of more than ordinary significance, for it tends to consolidate, in interesting and easily understandable terms, the history and definitions, not only of the now-standard oil barrel but also of the units that make it up and the legal pitfalls connected with it. It is a story full of oil-drilling lore--about odd-sized barrels in wagons for transporting the newly discovered petroleum in Pennsylvania in 1859; about Benedict Hagan, who supplied many an empty whiskey barrel to the producers at Oil Run; about Nelly Bly, who is more redoubtable to the oil industry for having been the "mother of steel barrels" than for besting Phileas Fogg's time in circling the globe; about the scientific struggle for accuracy in gauging oil. The Oilman's Barrel has important meaning for historians, metrologists, petroleum lawyers and executives, coopers, distillers, and the petroleum industry generally.