Almost everything can be, and is, sent by container ship, Zampa says. From palm trees to racehorses.

“You name it, you’ll find it in a container," he says.

Ship Size Matters

As for the ships, they keep getting bigger to handle more volume. The biggest ships are longer than the Empire State Building is tall.

"If you tip the Empire State Building on its side, the biggest ships coming to Oakland are bigger,” Zampa says.

Your average ship can hold about 14,000 containers. Last year, the biggest ship that came to Oakland could hold more than 18,000 containers. According to the BBC, a ship that big could fit 36,000 cars or 863 million tins of baked beans.

This is one of the reasons shipping by sea is more efficient than shipping by air, Zampa says.

“If you put all that cargo on airplanes, how many airplanes would it take? I couldn’t tell you," he says. "But that’s a lot more exhaust being emitted."

Comparing the cargo space of an average freighter ship to the cargo space of a 747 airplane, it would take roughly 630 planes to move as much as a single ship. The difference is time. On average it takes a couple of weeks for a container ship to cross the Pacific from Asia.

A 'Star Wars' Connection?

We've been asked if the cranes at the port inspired George Lucas to create the AT-AT snow walkers in "The Empire Strikes Back." It turns out that they did not.

Zampa says the port is still special, just not in a Hollywood way. One way it stands out is that this American port exports more than it imports. And that's not the case with most other U.S. ports.

"Most other U.S. ports are heavily skewed toward imports," Zampa says. "That reflects the trade imbalance that the U.S. has with the rest of the world."

Imports mostly come from Asia via Southern California.

What's in the Containers?

Imports include apparel, consumer electronics, consumer goods, glass and a variety of household items.

The Oakland port exports lots of dried fruits and nuts, wine and other beverages.

Zampa says demand from Asia is growing for American farm products.

"Their middle-class populations have exploded, and as the middle class develops, it develops middle-class tastes," he says.

Another major export out of Oakland? Paper.

That's because of all the cardboard boxes we use to package our goods.

“If you think about it, everything you buy is going to come in a cardboard box," Zampa says. "The West Coast sends a lot of scrap paper to Asia to make cardboard boxes that then get filled with goods and shipped back here."

The port's busiest season comes in late summer and early fall as American retailers stock up for the holidays. Last year, the port's busiest month was August, when more than 220,000 containers came or went.

Why Not San Francisco?

San Francisco was once the major port in Northern California, but when container shipping emerged, Zampa says San Francisco no longer had the land to handle containers. Oakland did. Today there are hundreds of acres of land devoted to container shipping.

The Oakland port has the advantage of being close to lots of cities and easily connecting to railway lines. About 10 percent to 20 percent of the containers head on to rail, destined for places like Salt Lake City or Denver.

But the majority of the container cargo is loaded onto trucks and taken to destinations in Northern California and western Nevada.