SEATTLE — Jeremy Peña homered in the 18th inning, and the Houston Astros beat the Seattle Mariners 1-0 on Saturday to advance to the AL Championship Series for a sixth consecutive year.

Peña drove a slider from Penn Murfee deep to left-center for the rookie shortstop’s first playoff homer, providing the lone run in an afternoon full of dominant pitching and empty trips to the plate. The 18 innings matched the longest game in playoff history. The game lasted 6 hours and 22 minutes.

“Man, that was a long game. But you still got to lock in, try to put together good at-bats,” Peña said. “I was just trying to stay inside the baseball, drove it in the gap.”

Spoiling Seattle’s first home playoff appearance since 2001, Houston completed a three-game sweep of the ALDS. Next up is the New York Yankees or Cleveland Guardians in Game 1 of the ALCS on Wednesday.

While Yordan Alvarez got the big hits in the first two games in Houston, it was Peña that set the table for Alvarez’s opportunities. As Game 3 made its way into its sixth hour, Peña delivered another painful blow to the Mariners that ended their short return to the postseason.

After 21 years, Seattle fans welcomed playoff baseball back to town. They got their money’s worth, and then some.

Three previous playoff games reached the 18th inning before conclusion, one involving Houston. The Astros beat the Atlanta Braves 7-6 in 18 innings in Game 4 of the 2005 NLDS on Chris Burke’s game-ending homer.

Game 2 of the 2014 NLDS between San Francisco and Washington and Game 3 of the 2018 World Series between Los Angeles and Boston also went 18 innings.

But those games had runs. This one failed to produce anything until Peña’s swing on a 3-2 pitch.

“I feel like in the playoffs you can’t try and do too much, especially the later the game goes,” Peña said.

Seattle’s best scoring chance was Julio Rodríguez’s line drive that thudded off the wall in the eighth inning. Seattle had runners in scoring position in the 13th and 17th, but couldn’t get a key two-out hit against Houston’s superb bullpen.

Unlike baseball’s regular season, there is no automatic runner when playoff games go to extra innings.

Luis Garcia worked five innings for the win. The Astros bullpen allowed five hits and struck out 15 following six innings from starter Lance McCullers Jr.

“Watching the whole thing the guys are doing a really good job and I’m really proud of them. … I was just trying to help,” Garcia said.

Seattle’s bullpen was nearly as good. After rookie George Kirby threw seven innings, nine Mariners relievers combined for 11 innings of five-hit ball.

The teams combined to strike out 42 times, topping the postseason record of 39 set by the Guardians and Rays last week in their AL wild-card matchup that was scoreless for 15 innings before Oscar Gonzalez’s home run sent Cleveland to the ALDS.

“Their pitching was phenomenal today as well,” Seattle manager Scott Servais said. “We kept putting the zero up there and kept putting the zero up there and you think we’re going to be able to break through because we have so many times. It’s kind of what we’re accustomed to playing — those tight games and finding a way but there were no errors made in that game today.”

Houston advanced despite a rough performance for Jose Altuve, who went 0-for-8 in Game 3 for the first time in his career and was hitless in 16 at-bats in the series.

Altuve joined Xander Bogaerts in Game 3 of 2018 World Series versus the Dodgers as only players to go 0-for-8 or worse in a postseason game. But Houston’s other pieces came through, none bigger than its young shortstop who took on a prominent role after Carlos Correa departed in free agency.

Peña’s homer was his lone hit in eight at-bats. But it was his contributions in the first two games that helped Houston travel to Seattle with a 2-0 lead in the series.