The United Nations Environment Programme (UNEP) North America Office, the Mississippi River Cities and Towns Initiative (MRCTI), the University of Georgia’s Debris Tracker, National Geographic Society, and other local and national partners worked together on a pilot study for the Mississippi River Plastic Pollution Initiative to generate a first-ever snapshot of the state of plastic pollution along the Mississippi River. The data was generated through a ‘citizen science’ approach, enlisting the participation of hundreds of community volunteers covering targeted areas along the river to understand the movement and accumulation of plastic pollution. Debris Tracker, an open data citizen science movement and free mobile phone app, was used to collect the data. Three cities participated in the pilot study: Baton Rouge, Louisiana; St. Louis, Missouri; and St. Paul, Minnesota. The data gathered in the basin, along the river and in the pilot communities was examined to understand the state of plastic litter in these river cities. The goal was to generate as rich a picture as possible, within a dedicated timeframe, of the extent and type of litter that can make its way to the river.