Mitch Megginson's 75th-minute strike was enough for Rangers to finish top of the table and earn promotion to the Championship.
It is the second time in three years that Paul Hartley’s men have earned promotion, having joined the senior ranks in 2019/20.
Second-placed Airdrieonians continued their quest for promotion with a 5-0 win against Clyde.
Airdrie were awarded a penalty in the 35th minute and Rhys McCabe slotted home to give them the lead.
Second-half goals from Callum Smith, Calum Gallagher, Kyle MacDonald and Jonathan Afolabi ensured the Diamonds secured back-to-back league wins.
Two quick second-half goals saw Montrose come back to beat Queen's Park 2-1.
Connor Smith put the Spiders ahead inside the first minute, slotting the ball into the bottom corner.
Montrose then equalised through an own goal from Michael Doyle in the 78th minute before Sean Dillion sealed the three points three minutes later.
Peterhead continued their revival in the league by making it five games unbeaten with a 1-0 win against already-relegated East Fife.
The hosts took the lead through Jack Brown in the 11th minute after a shot from the edge of the box found the bottom left corner.
Alloa returned to winning ways with a 2-1 win against Falkirk.
The Wasps took the lead inside the opening 10 minutes through Kevin Cawley and Conor Sammon doubled the lead in the second half before Anton Dowds pulled one back for the Bairns.