Why LA/Long Beach dominates, and when freight shifts east

The Port of Los Angeles and the Port of Long Beach together form the largest container gateway in the US, and the reason is geography. The two ports sit side by side on San Pedro Bay, and San Pedro Bay is the closest major port complex to the factories of East Asia, where the bulk of US containerized imports are made. The complex has historically handled on the order of 40 percent of the nation's containerized imports, though that share has eased in recent years as freight has spread to other coasts.

Why the West Coast gets the boxes first

Transpacific geography does most of the work. A box leaving a Chinese port reaches Southern California days faster than it reaches the East Coast, which sits an ocean and a canal transit farther away. For an importer moving goods to inland distribution, landing on the West Coast and railing east has long been the fast lane. Scale compounds it. Because so much cargo already flows through LA/Long Beach, the terminals, the rail connections and the drayage capacity have built up around them, and that infrastructure pulls in still more cargo.

What sends freight east

The West Coast advantage is not permanent, and cargo shifts when the math tips. Three factors move it. Labor, because West Coast dockworker contract cycles have in the past made importers wary of a work stoppage and route cargo to the East Coast as insurance. Canal economics, because an all-water route to the East Coast through the Panama or Suez canals competes on cost when it runs smoothly and suffers when draft limits or conflict force reroutes. And rates, because when the price gap between West Coast and all-water services narrows, some importers pick the coast closer to their customers.

Watch the shift in the volume

The chart above is the Los Angeles loaded-import stream, the clearest West Coast demand read on this site. A coast-to-coast shift does not announce itself, it shows up slowly here and in the matching East Coast numbers, one gaining share while the other gives it up. This site reports those moves as they land in the data, month by month. It does not predict which way share goes next, because that turns on labor talks, canal conditions and rate spreads that are nobody's to forecast honestly.

The Dwell reports port volumes and share as the authorities publish them, dated to the month. It does not forecast freight patterns and it is not routing advice. For the East Coast comparison, see the Port of NY/NJ volumes. For the unit these counts use, see what is a TEU.