Washington State finished No. 9 in both national football polls Sunday, and USC officially topped the Associated Press rankings.
The Cougars climbed six spots after upsetting fifth-ranked Texas in the Holiday Bowl last Tuesday.
The No. 9 ranking for WSU comes after back-to-back No. 10 finishes the past two seasons.
Southern California finished No. 1 in The Associated Press poll, earning 48 of the 65 first-place votes.
The Trojans (12-1) beat out USA Today/ESPN coaches' poll champion LSU, which defeated Oklahoma 21-14 in Bowl Championship Series title game Sunday night in the Sugar Bowl.
The coaches were obligated to crown LSU (13-1) even though USC held the top spot in their poll going into the bowls.
It's the first split national championship since 1997 when Michigan won the AP poll and Nebraska was the coaches' choice. The BCS started the following season with the goal of choosing an undisputed champion.
In each of the first five years, only one major team finished undefeated, making the choice simple. But with three top one-loss teams at the end of the regular season, chaos reigned.
USC was left out of the BCS title game despite being the top team in both polls, while Oklahoma made it after losing the Big 12 championship game 35-7 to Kansas State.
The Trojans, who beat Michigan 28-14 in the Rose Bowl on New Year's Day, have now been involved in three of the 11 split titles in college football history. In 1978, they won the coaches' poll while Alabama won the AP poll, and in 1974, the coaches picked USC while the media picked Oklahoma.
The Trojans hadn't won the AP poll since 1972, when they were the undisputed champion. That was also the last time a Pac-10 team won the AP title. Washington won the coaches' poll in 1991.
USC has four AP titles overall, tied with Minnesota, Nebraska and Ohio State for the fifth most ever.
There have been nine different champions in the past nine seasons, the longest stretch in the history of the poll.
In the final, post-bowl AP poll, USC received 1,608 points to beat out LSU (1,576). Oklahoma was third, followed by Ohio State and Miami.
Coach Pete Carroll won the title in his third year at USC, capping the Trojans return to prominence after years of mediocrity. The Trojans went 31-29 in the five years before Carroll arrived in Los Angeles. After losing five of his first seven games, Carroll is 27-4.
The Trojans began this season eighth in the poll and made it up to third before losing 34-31 in triple overtime to California on Sept. 27. After falling to No. 10, USC worked its way up the poll and took over the top spot in the final regular-season poll.
Michigan, Georgia, Iowa, Washington State and Miami of Ohio rounded out the Top 10.
Florida State was next, followed by Texas, Mississippi, Kansas State, Tennessee, Boise State, Maryland, Purdue, Nebraska and Minnesota.
Utah, Clemson, Bowling Green, Florida and TCU rounded out the poll.
The SEC and Big Ten led all conferences with five teams apiece, followed by four for the Big 12, three for the ACC, and two each for the Pac-10 and Mid-American.
The Big East, WAC, Mountain West and Conference USA each had one team, leaving the Sun Belt conference as the only Division I-A league without a team in the final poll.