Mississippi River Locks: How Grain Barges Carry Midwest Corn to the World

A kernel of corn from Iowa can end up feeding a chicken in Japan. But first it rides a truck to a river elevator, a barge down the Upper Mississippi's staircase of 29 lock-and-dam sites, and the open river to the export elevators near New Orleans, the route that carried 48% of U.S. grain inspected for export in 2024. We follow the journey, explain why 15-barge tows have to split in half at most locks, and look at what happens when the river runs dry: four low-water harvests in a row, and a record $105.85 a ton to move grain from St. Louis. In this episode: 0:00 One kernel, one staircase of water 0:33 Harvest and the truck line 1:24 The barge: 1,500 tons, no engine 2:16 The staircase: 29 locks and dams 3:48 Winter: the river closes 4:19 Below St. Louis: open river, giant tows 5:13 When the river runs dry 6:31 The Gulf: where barges become ships 7:14 Panama, Asia and Brazil 8:10 How we know, myths, and what we don't know Quick answers: • How much does a grain barge carry? About 1,500 tons at a 9-foot draft, roughly 16 rail cars or 70 semi-trucks (TTI for the National Waterways Foundation). • How many locks are on the Upper Mississippi? 29 lock-and-dam sites between Minneapolis and St. Louis; Upper St. Anthony Falls has been closed to navigation since 2015. • Why do barge tows split at locks? A 15-barge tow is about 1,200 ft long, and most chambers are 600 ft, so it goes through in two pieces (a "double lockage"). • How much U.S. grain goes down the Mississippi? In 2024, 48% of grain inspected for export left via the Mississippi Gulf; the Pacific Northwest handled about 28% (USDA AMS). SOURCES • USDA AMS, A Reliable Waterway System (April 2025): https://ams.prod.usda.gov/sites/defau... • USDA AMS Grain Transportation Reports (Nov 10, 2022; Aug 6, 2026): https://www.ams.usda.gov/sites/defaul... • USDA AMS, Export Elevator Overview: https://www.ams.usda.gov/resources/ex... • USDA WASDE, August 2026: https://www.usda.gov/oce/commodity/wa... • National Academies, Upper Mississippi River navigation (NAP 10072): https://www.nationalacademies.org/rea... • USACE St. Paul District, 9-Foot Channel Project: https://www.mvp.usace.army.mil/Home/P... • USACE Rock Island District, Lock and Dam 19 fact sheet: https://www.mvr.usace.army.mil/Portal... • USACE St. Louis District, Lock and Dam 25 1,200-ft lock project: https://www.mvs.usace.army.mil/Missio... • USACE St. Louis District, Lock 27 fact sheet: https://www.mvs.usace.army.mil/Portal... • Federal Register (2014), Closing Upper St. Anthony Falls Lock: https://www.federalregister.gov/docum... • USACE St. Paul District (DVIDS), navigation season 2025–2026: https://www.dvidshub.net/news/552467/... • TTI for the National Waterways Foundation (2022): https://www.nationalwaterwaysfoundati... • farmdoc daily, University of Illinois (Nov 2022): https://farmdocdaily.illinois.edu/202... • NASA Earth Observatory, Drought and barge backups (2022): https://science.nasa.gov/earth/earth-... • Farm Policy News, University of Illinois (Oct 2025): https://farmpolicynews.illinois.edu/2... • American Farm Bureau Federation, shipping chokepoints: https://www.fb.org/market-intel/chaos... • USDA AMS, Brazil soybean transportation Q2 2025: https://www.ams.usda.gov/sites/defaul... VISUALS & LICENSES Photos: U.S. Army Corps of Engineers, USGS, USDA (incl. Preston Keres), NASA, NOAA National Weather Service, National Park Service, National Archives, Historic American Engineering Record: public domain. Other photos from Wikimedia Commons, public domain or CC0 (credited on screen). Maps, charts and diagrams made by How Things Arrive from the sources above; base map Natural Earth (public domain); diagrams are not to scale. NARRATION & MUSIC Narration uses AI voice technology (ElevenLabs). Research, script and fact-checking by How Things Arrive. Music: "Laniakea" by The Grey Room / Density & Time, YouTube Audio Library. How Things Arrive: the hidden journeys behind everyday life. New documentaries every week. #MississippiRiver #SupplyChain #Documentary