ESPN ranked the 20 most unlikely national title winners of the past 75 years.

Clemson’s 1981 national championship team (12-0) landed near the top of the list, coming in at No. 6.

The 1981 Tigers went on an unprecedented run in Clemson history. They beat No. 4 Georgia, No. 8 North Carolina, and No. 4 Nebraska on their way to winning the school’s first national championship in any sport.

Here’s what ESPN’s Bill Connelly wrote about the Tigers’ 1981 squad, which was unranked in the preseason AP Poll and spent just one week at No. 1 in the AP Poll:

“Clemson had gone just 14-9 in young head coach Danny Ford’s first two seasons, hinting at major defensive upside and pummeling a couple of ranked teams but struggling with consistency. The Tigers were unranked heading into their Week 3 matchup with Herschel Walker and No. 4 Georgia, but a 13-3 upset of the defending champs triggered a rapid rise. They were ranked second heading into November, and they moved to No. 1 for the first time ever following top-ranked Pitt’s blowout loss to Penn State. They were four-point underdogs against No. 4 Nebraska in the Orange Bowl — a sign that they weren’t being taken seriously enough — but a 22-15 win gave them their only title until 2016.”

Since 1962, Clemson’s 1981 team is one of just three teams to claim an AP National Championship after opening the season unranked.

Overall, the Tigers finished second nationally in scoring defense in 1981, seventh in rushing defense, seventh in turnover margin and eighth in total defense. Clemson led the ACC in total defense, rushing defense, scoring defense and interceptions. It forced a school record 41 turnovers.

Clemson allowed just three teams to score more than 10 points in 1981 — Wake Forest, South Carolina and Nebraska — and it went 18 quarters without giving up a touchdown during one stretch.