Sebastian Blanco scored in the 86th minute and the Portland Timbers beat the Seattle Sounders 1-0 on Sunday in the 100th match between the rivals.
The rivalry dates to 1975 in the North American Soccer League and gained national attention when the Timbers joined the Sounders in MLS in 2011.
Blanco's late goal helped the Timbers extend their winning streak to four games, after the failed to earn three points in any of their first five games of the season. The Timbers haven't lost in five straight at home against the Sounders.
Both sides had chances in the first half. Diego Valeri's shot for Portland in the 39th minute went wide left, and Clint Dempsey's attempt five minutes later for Seattle was too far right.
There were also a few notable yellow cards, the first on Seattle's Jordy Delem in the 34th minute that the crowd at Providence Park clearly thought was worthy of a red. There was another yellow for Timbers defender Liam Ridgewell in the 44th minute, and Alex Roldan was booked for fouling Valeri for in the 75th.
Portland's Andy Polo had a shot in the 68th minute that was stopped by goalkeeper Stefan Frei.
Blanco broke through, charging at Frei and then perfectly placing an angled shot from just outside within the left post for his team-leading fifth goal.
"Always, it's important to win this game," said Blanco, who brought his Chucky mask from his native country. "It's a derby. It's a different game. It's a different game in MLS. We played some moments good, we played some moments bad, but I think we dominated the whole game."
Sounders coach Brian Schmetzer was clearly frustrated afterward .
"It's a tough loss. Tough pill to swallow. I think the guys put everything into the game. Look, the goal was a well-crafted goal, I'll give them some credit. Blanco was a good finish. But I thought there were some times in the game we had the upper hand. Second half was back-and-forth. It's disappointing, disappointing to lose that late in the game, disappointing to lose to Portland. Simple as that."
When MLS granted franchises to Portland and Vancouver, the league hoped to build on the regional rivalry already in place in the Pacific Northwest. The trio already played for the Cascadia Cup, a three-way competition based on points that was created by supporters of the teams in 2004, when they were all part of the USL.
Sunday's match did not count toward the Cascadia Cup because this year the MLS schedule between the teams is unbalanced, so one of the games between the Timbers and the Sounders had to be thrown out.
It was possible that Portland midfielder David Guzman would return for the Sounders match, but he was not available. The 28-year-old Costa Rican sprained his knee during international duty at the end of March, and the national team has been careful about his return because he'll likely figure into the team's World Cup plans.
On Seattle's side, Roman Torres has a hamstring injury that is expected to sideline him for some four weeks and could put his chances of playing for Panama at the World Cup in jeopardy.
Also missing was Nicolas Lodeiro, who is nursing a fractured toe. Lodeiro is also a possible national team call up for Uruguay. The deadline for the 32 World Cup teams to announce preliminary rosters is Monday.
The Timbers got off to a rocky start this season under new coach Giovanni Savarese. They were winless in their first five matches, which were all played on the road because of the ongoing expansion project at Providence Park. But Portland had since won three straight, including last weekend's 1-0 victory at San Jose.
"We knew it was going to be difficult, as it was," Savarese said. "These kind of games are battles. Just proud of how these guys continued to battle and how these guys continued to be disciplined."
The Sounders were struggling with just one victory in seven games to start the season, falling into last place in the Western Conference. But they got a boost with a 2-1 victory against Toronto -- their MLS Cup rivals -- on the road on Wednesday night.