The Oakland Athletics routed the Texas Rangers 12-5 to secure Major League Baseball's American League West title for the first time in six years.
The New York Yankees were also celebrating Wednesday night as they claimed their 13th AL East crown in 17 years with a 14-2 victory over the Boston Red Sox.
The win also gave New York (95-67) the best record in the AL and home-field advantage throughout the league postseason.
The Yankees will face the winner of Friday's wild card contest between Baltimore and Texas in the division series, which starts Sunday.
Oakland stood 13 games behind the Rangers on June 30, but the Athletics have gone an MLB-best 57-26 since then.
That included their three-game season-closing sweep of the Rangers to clinch the 15th AL West crown in team history.
"We knew this is a beast of a team we would have to beat, and to be able to beat them three games in a row and win the division on top of it, really it's a magical type thing," A's manager Bob Melvin said.
Coco Crisp drove in two runs and scored twice in Wednesday's game, while Brandon Moss added three RBIs and a run scored for the A's.
A's pitcher Evan Scribner earned the win after throwing three scoreless innings in relief of starter A.J. Griffin. Griffin allowed five runs on seven hits in just 2 2/3 innings. Four of the five runs he allowed were earned.
Slugger David Murphy knocked in two runs and Adrian Beltre drove in one run for the Rangers, who will continue their quest for a third-straight World Series appearance when they play in a wild card game on Friday.
Baltimore finished second in the AL East after losing to Tampa 4-1 on Wednesday.
"You never know," said outfielder Josh Hamilton. "This could be a blessing in disguise."
Hamilton dropped a fly ball in the outfield for a two-run error that put Oakland ahead 7-5 in a six-run fourth inning.
Pitcher Derek Holland suffered the loss after giving up three runs on three hits and two walks in 2 2/3 innings of relief. Holland won 12 games and lost seven this season.
"You can have all the experience as you want but when you run into a team that is hot, experience has nothing to do with hit," said Rangers manager Ron Washington.
The A's are just the third team in MLB history to win a division while spending just one day in sole possession of first, joining the Minnesota Twins (2006) and the Giants (1951).
Japan's Hiroki Kuroda pitched seven solid innings and Robinson Cano and Curtis Granderson each homered twice as the Yankees crushed the Red Sox.
Cano led a 15-hit assault by going four-for-four with three runs scored and tying a career-high with six RBI.
Granderson drove in four runs for New York, which has belted a league-best 245 home runs to eclipse the franchise's previous season record of 244.
Kuroda (16-11) did his part by limiting Boston to just two runs and scattering seven hits. He is an impressive 4-1 over his last six starts.
Red Sox starting pitcher Daisuke Matsuzaka (1-7) was roughed up for five runs and six hits in just 2 1/3 innings. Japan's Matsuzaka, who finished with a dismal 8.13 earned run average, was likely making his last start of a lucrative six-year contract with Boston.
"I didn't expect the six years to end the way it did end," said Matsuzaka.
"There were some great memories -- the first year winning the World Series was great.
"But I wasn't able to perform to my expectations after the first two years, so I'm really disappointed and I'm really apologetic that I wasn't able to perform to my expectations."
Cody Ross went two-for-three with an RBI single for Boston.