AbstractThe USACE, St. Louis District, is responsible for maintaining navigation channels along with multiple lock and dam structures on the Mississippi River, a vital inland waterway that carries millions of tons of commodities every year. Understanding commercial vessel traffic patterns is fundamental to informing decisions about construction projects and to efforts to improve communication to mariners. Automatic Identification System (AIS) data provides time-stamped and geo-referenced vessel position reports for most commercial vessels operating in the District’s area of interest. This paper describes how AIS data has been successfully used by St. Louis District waterway managers to (1) prevent conflicts with the navigation industry by revealing active fleeting areas that were under consideration for the construction of river training structures; and (2) identify changes in vessel approaches to a lock structure under different river flow conditions, providing operational information that could be used in future navigation alerts to mariners. This paper concludes with a list of suggested best practices for waterways managers who want to start, or expand, their use of AIS data.