Port of Charleston container ships

Two container ships capable of carrying 14,000 cargo boxes apiece have plenty of room to pass during visits this month to the Port of Charleston. The port was the nation's 8th-busiest in 2017, according to industry analyst Alphaliner. Provided/State Ports Authority

The Port of Charleston was the 8th-busiest seaport in the United States last year with nearly 2.2 million cargo containers moving through its terminals, industry newsletter Alphaliner said in its annual global ranking.

Charleston maintained its ranking ahead of the Port of Seattle — 1.42 million cargo containers in 2017 — and behind the Port of Tacoma, which handled 2.25 million.

Alphaliner bases its figures on 20-foot-long increments, a standard way for the maritime industry to count containers.

The Port of Charleston saw 9.2 percent annual growth in containers in 2017, the nation’s third-highest percentage increase. Its eighth-place overall U.S. ranking was unchanged from last year.

The port has seen a year-over-year decline in containers so far this year but expects to make up the volume in coming months.

"Our container volumes are on track leading into spring, which is generally a strong season for the port," said Jim Newsome, president and CEO of the State Ports Authority.

The arrival of big ships traveling through the expanded Panama Canal has led to a boom in cargo for East Coast ports, with Charleston setting a record for containers handled at its terminals in 2017. Its counterpart in Savannah also set an annual record with an 11 percent rise.

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The combined ports of Los Angeles and Long Beach were the nation's busiest in 2017, handling 16.89 million containers.

Globally, the Port of Charleston was the 78th-busiest container port. The Port of Shanghai, which handled 40.23 million cargo boxes last year, was the world's busiest.

Of the world's top 110 ports, 20 are located in China, followed by nine in the U.S. and five in Japan, according to Alphaliner.

All told, the world's 110 busiest ports handled a combined 600 million containers in 2016 — a 6.1 percent increase over the previous year.

Reach David Wren at 843-937-5550 or on Twitter at @David_Wren_