Derby County sealed promotion back to the Championship after two seasons away with a 2-0 win over already-relegated Carlisle United on League One's final day.
Needing only a draw to join Portsmouth in winning automatic promotion, the Rams won thanks to goals by Max Bird and James Collins, consigning Bolton Wanderers to the play-offs.
Thousands of jubilant Derby fans invaded the Pride Park pitch and chanted 'we are going up' at the final whistle as Paul Warne completed his fourth promotion up from League One after three previously with Rotherham United.
Meanwhile, Oxford United claimed the one remaining play-off berth ahead of Lincoln City and Blackpool, while Cheltenham Town suffered relegation to League Two after a 2-1 loss at Stevenage.
It was a cathartic day for Derby, who suffered relegation into League One while in dire financial straits in 2022, as they secured only a second promotion in 26 years.
It took just five minutes to begin the party when Bird, making his 200th and final Derby appearances before he joins Bristol City, fired past Harry Lewis from 20 yards.
Carlisle's fate may already have been sealed but they were determined not to go quietly as Jack Armer forced Joe Wildsmith into a near-post save.
Ebou Adams thought he'd scored on the half-hour but the midfielder had strayed offside after Louie Sibley's shot was blocked.
Wildsmith was called upon again to touch over Georgie Kelly's header but the nerve-settling second arrived just before the hour mark.
Wildsmith's long free-kick was headed down by Sonny Bradley and Collins smashed in his 19th of the season from eight yards so the promotion champagne could be uncorked.
It seemed the bulk of the sold-out 31,027 crowd were on the pitch after the final whistle as Derby lifted the runners-up trophy.
It was still possible at kick-off for Ian Evatt's Bolton to snatch second spot from the Rams but Derby's win rendered that academic and the Lancashire side could only draw 3-3 at play-off bound Peterborough.
Bolton started in electric fashion when Kyle Dempsey headed them in front after only four minutes from Randell Williams' left-wing cross.
That advantage was quickly doubled when Dion Charles sent Posh goalkeeper Jed Steer the wrong way from the penalty spot after Hector Kyprianou brought down Williams.
But Posh launched a stunning second-half fightback after Malik Mothersille tapped in a David Ajiboye cross after 50 minutes.
Joel Randall then raced clear onto a pass by Ephron Mason-Clark to bring the hosts level on 67 minutes.
With news of Derby's second goal filtering through, Posh went ahead when Randall turned provider for Mothersille to score again.
Bolton salvaged a draw when substitute Nathanael Ogbeta's cross was converted by fellow replacement Cameron Jerome and the two teams could yet meet again in the Wembley final.
The play-off semi-finals will see Bolton take on Barnsley, who were held 1-1 at Oakwell by Northampton Town on Saturday.
Oxford won 2-1 at Exeter thanks to goals by Mark Harris and Cameron Brannagan to book their play-off date with Peterborough.
They finished ahead of Lincoln, beaten 2-0 at home by Portsmouth, and Blackpool, who lost 3-2 at Reading.
Cheltenham join Carlisle, Port Vale and Fleetwood Town in being relegated to League One after their 2-1 loss at Stevenage.
Matt Taylor cancelled out a Kane Hemmings penalty, but Nick Freeman's late winner sealed Cheltenham's fate.
It meant Burton Albion stayed up despite a 3-0 loss at Fleetwood, likewise Cambridge who drew 0-0 at Port Vale.