Jim Shaughnessy: Essential Witness is a comprehensive overview of Shaughnessy's sixty year as a railroad photographer. Starting in the late 1940s, he began documenting in earnest the rapidly changing railroad scene in the Northeastern United States. His interests and travels also took him to other areas of the country to document the Rio Grande narrow gauge in Colorado and the UP Big Boys in Wyoming, and various locations in Canada. His timing was perfect: he was there to record the dramatic transition between the steam and diesel eras as well as documenting and recording for posterity the workers behind the machines that operated in the depots, roundhouses and back shops of the American railroad environment. Lucius Beebe once described Shaughnessy as 'a master in the massive effects of black and white.'

The book includes some 150 duotone photographs taken between 1948 and 1970, with the emphasis on the 1950s and 1960s. Images include landscapes, cities and towns; action shots of formidable trains barreling down the tracks; snaps of weary railroad workers; nighttime photos of shadowy enclaves within the railyard; and many more.