Round goby (Neogobius melanostomus) are invasive benthic fish native to the Black and Caspian Seas of Eurasia. First documented in the Chicago Area Waterway System in 1993, this aggressive species has been progressing from Lake Michigan toward the Mississippi River via the Illinois River. Here we describe the history of round goby monitoring in the Illinois River and the more recent annual efforts by the U.S. Fish and Wildlife Service to document the expansion of round goby toward the Mississippi River using multiple gears. From 2014 to 2017, annual monitoring has documented the expansion of round goby in the lower Illinois River to within 55 rkm of the Mississippi River, beyond previously published capture locations. Although it is unclear whether or not round goby are reproducing this close to the Mississippi River or if a population is established, their presence is concerning considering their deleterious impacts to native species in other systems. Additionally, the Mississippi River and its tributaries provide an abundance of preferred spawning habitats that could facilitate the expansion of self-sustaining populations throughout the Upper Mississippi River watershed. We urge the development of more robust monitoring and management strategies designed to identify and mitigate the potential impacts of this species.