This map shows the flow of all domestic freight between states in 2015 using data from the Freight Analysis Framework, which is a comprehensive accounting of all commercial freight movement between states by all modes of transportation. This includes freight moved by trucks, trains, planes and pipelines, but excludes foreign imports and exports and freights transported within a state.
How to read it: The arrows represent the origin and destination of goods shipped between states. Thicker and darker arrows indicate higher volume (each commodity is scaled relative to the highest volume between any two states, so arrow size isn't comparable across commodities).
Some relationships are head-scratchers at first glance. For instance, the Alcoholic beverages category shows an outsize role for Iowa, which is not necessarily known for its beer and wine industry. But the full category description covers "denatured" alcohol, which includes corn-based ethanol.
Some anomalies may be explained by steps within a supply chain. A manufacturer in California may ship to a wholesaler in Missouri, who then ships to a retailer in Texas. Some raw materials go through a distillery or rendering process before shipping elsewhere for sale or consumption. But then why is so much building stone shipped from Texas to Alabama?
Do you have an explanation for other state-to-state routes that look out of place? Send me an email at email@example.com. I'd love to hear from you.
What else we saw:
- Nearly 16 million kilotons of domestic goods shipped within the United States in 2015.
- Fossil fuels are by far the most-shipped commodity within the United States. Coal, gasoline, fuel oils and natural gas represent one-third of all freight traffic in 2015.
- Twenty-eight percent of all plastics and rubber transported in America flow out of Texas
- The vast majority of coal in the U.S. is produced in Wyoming — not Appalachia — and shipped within the Midwest.
- Most metallic ore comes from Minnesota, which is the highest producer of iron ore.
- Thirty-nine percent of all pharmaceuticals shipped originated from California, Texas, New Jersey and Pennsylvania. New Jersey to California represents the highest-volume state-to-state route.