U.S. pork processing capacity grew more on one day last week than any single year in memory — and perhaps ever — with the opening of new packing plants in Sioux City and Coldwater, Michigan, on Sept. 5, according to Steve Meyer, vice president of pork analysis for Express Markets Inc. Analytics.

"The only reason I am not more certain of an ‘ever’ designation is that we don’t have records of when the old plants opened in the late-1800s and early 1900s. Given those plants’ relatively small size, I think the statement is safe," Meyer said.

The Triumph-Seaboard plant in Sioux City and the Clemens Food Group plant in Coldwater add 22,200 head of slaughter...