The container fell off the truck at about 8:15 a.m. near 18th Avenue South. After hitting the pavement, the container rolled over onto its side and skidded about 200 feet, leaving a trail of drag marks and manure.
Troopers immediately responded to the scene, where they found that many of the cattle had died in the crash and some of the surviving cattle still had their hooves stuck in the container's barred windows.
"I've never seen this happen here, no," said Sgt. Joseph Zimmer of the State Patrol.
Authorities didn't want to release the remaining cows from the container, due to concerns they might immediately wander off into freeway traffic.
The only other option was to right the container with the cattle still inside, so two large tow trucks were brought in, and they slowly righted the container.
"It was a pretty big mess," said John Halberg, of GT Towing Service. "When State Patrol called, they asked if we could do a nice, slow, controlled roll to keep the casualties down."
Once the container was upright, it was loaded onto another trailer. The cattle were then trucked to Sunnyside, in Central Washington, to be inspected by a veterinarian.
"We've discussed some options on what to do with the injured and deceased cows in the interim, and really our only option is to continue on to Sunnyside," Zimmer said.
The shipment had just arrived from Hawaii at the Port of Seattle. That's where the State Patrol says the truck driver may have attached the trailer incorrectly or used faulty equipment.
Some lanes of I-90 were closed for about three hours during the incident, causing minor traffic delays.
The accident remains under investigation. Troopers say the truck driver, a 53-year-old Bellingham man, was not speeding when the trailer flipped.
It was not immediately known whether charges would be filed against him.