The 55,718 crowd they attracted to the weekend's 2-0 win over Vancouver Whitecaps has them with an average crowd pull of 42,578 per game at their home ground, CenturyLink Field.
The attendance figure on Saturday made it the third time the Sounders had won in front of more than 50,000 fans and head coach Sigi Schmid was thrilled to again come up with the goods in such a big game.
"It's a tremendous reflection of what Seattle is doing," Schmid said.
"I told Adrian [Hanauer, Sounders general manager] if he keeps getting more than 50,000 we'll keep winning because every league game over 50,000 we've won.
"So we don't mind if in the next game they want to open up some more seats and get another 55,000 in there."
And Sounders midfielder Brad Evans was also delighted to be part of a franchise who are completely dominating the attendance ranks in North America.
"I think back to 2008 when I first found out I was coming here, then hearing there were 5,000 then 10,000 season-ticket holders," Evans said.
"All of a sudden, four years later, it's 55,000 for a league game. That's unheard of and it's really something special. As long as we keep winning these games we keep people happy and that's pretty important as well."