Archibald Geikie played a fundamental, but largely unrecognized, role in the establishment of the Scottish oil shale industry by providing James ‘Paraffin’ Young with the critical information about the location, thickness and probable geographical extent of organic-rich shales during their field visit in 1858. Young subsequently used the observations to determine where to buy leases for commercial oil shale extraction and production before any competitors emerged. Geikie acquired his critical knowledge of the area whilst preparing the first map and memoir of the Edinburgh area published in 1859 and 1861, respectively. In 1866, Young’s Paraffin Light and Mineral Oil Company Limited opened the Addiewell works, the largest oil shale works in the world at the time. By the late 1860s, there were over 120 works distilling oil in Scotland, mostly from the shales of the Lothians. Eventually, more than 22 million gallons of crude oil a year were produced in the Midland Valley in an industry that employed c. 40 000 people. Although the Scottish oil shale industry eventually closed in the 1960s, Geikie’s legacy lives on through a better understanding of the geology of the Midland Valley and the renewed interest in extracting oil and gas from the shales buried beneath.