Seattle Sounders' clash with Portland Timbers is set to be watched by 67,000 fans.
If it surpasses the 67,052 that attended a 2011 exhibition against Manchester United, it will set a new high-water mark for the popular club.
"It's a great tribute to MLS and to the Northwest rivalries," Sounders coach Sigi Schmid said. "It's going to be an electric atmosphere."