This 328-page hardback volume printed by the Illinois State Geological Survey includes over 1200 full-color, high-resolution photographs of fossil specimens collected from the Upper Ordovician Platteville Formation in the Upper Midwest USA. The described and illustrated fossil assemblage includes exceptionally well-preserved sponges, corals, bryozoans, brachiopods, polyplacophorans, gastropods, bivalves, rostroconchs, cephalopods, trilobites, ostracodes, echinoderms, graptolites, cornulitids, hyolithids, macroalgae, and a wide variety of trace fossils.This overview is directed to students, collectors, and professional paleontologists. Each chapter begins with a brief introduction to the morphological terms used to describe the various fossil groups, followed by systematic descriptions, remarks, and occurrence information. This overview can serve as a starting place and a source of inspiration for future paleontological research on the fossils of the Platteville Formation, offer insights regarding past climate and the environments in which life thrived, and ultimately shed light on the history of life on our planet.Many Platteville fossils were described in pre-20th century reconnaissance reports commissioned by the state geological surveys of Illinois, Iowa, Minnesota, and Wisconsin. A historical summary of paleontological investigations of the Upper Ordovician stratigraphic succession can be found in Sloan (1987). A drawback to understanding the documented faunal composition of the Platteville Formation is that many of the fossils are described and illustrated in diverse monographs and shorter papers spanning more than 150 years and published by a variety of organizations. Many of these publications are difficult to find in libraries and are not available online. Furthermore, they tend to focus on specific phyla rather than the overall faunal associations. An added drawback is that many early publications lack high-resolution photographs, making it difficult to compare and contrast fossil specimens.