Taconite shipping had another great month in August thanks to global trade and a robust regional economy.

"U.S. iron ore exports to Asia continue at a brisk pace," Bruce Burrows, president of the Chamber of Marine Commerce, said in a statement. "Given current North American economic conditions, we're optimistic that Seaway cargo levels will top last year's performance."

Iron ore shipments are well above their five-year average and are on pace to match if not beat highs not seen since 2012. The Twin Ports contributed 2.2 million tons of ore in August, according to data from the Lake Carriers' Association, with Two Harbors shipping 1.9 million tons and Silver Bay sending about 915,000 tons.

Across the Great Lakes, iron ore shipments were up 10.1 percent over August 2016. Year to date shipments stand at 36.8 million tons at all ports along the St. Lawrence Seaway.

U.S. Steel restarting its Keetac plant - and shipping to unspecified third-party customers, some on the other side of the world - has helped pull the iron trade out of the slump it had in the past few years.

Other commodities have trended up as well, with coal having a slight resurgence from last year's low and limestone jumping above average for August.

Total shipments so far this year, according to the Lake Carriers' Association, are just off the five-year average at 50.4 million tons.