Sheffield United 2 (Lowton 39, Williamson 59)
Barnsley 2 (Haynes 15, 84)
A double from Danny Haynes meant the Reds bagged a point against the Blades - whilst also condemning United to League One football next season.
Bobby Hassell was back in the eleven at the expense of Reuben Noble-Lazarus, meaning Kieran Trippier had the freedom of the right-wing.
GOAL 15 minutes: Danny Haynes' cool finish sent the Reds into the lead.
GOAL 39 minutes: Matt Lowton heads home from close range for United's equaliser.
GOAL 59 minutes: A mistake from Steele allowed Williamson's drive to trickle over the line.
GOAL 84 minutes: Danny Haynes does it again and heads home a delightful Hill cross.
Williamson claimed the first shot of the match as he tested Steele with a low drive just before the clock ticked over a minute.
Mellis really should have opened the scoring on six minutes but blazed a golden opportunity over the bar after charging into the area.
It was a tremendous atmosphere as both sides enjoyed spells of possession in the South Yorkshire sunshine. Maguire was next to try his shooting boots on 11 minutes but blasted well over the top of Steele's bar.
The deadlock was smashed on 15 minutes Danny Haynes broke through onto a perfect ball forward and calmly slotted past Simonsen from 12 yards for his fifth Barnsley goal.
A scramble in the Barnsley area on 20 minutes was somehow cleared as the Blades looked to bag a certain equaliser from three yards through Quinn.
United were looking nervous at the back and confusion between Maguire and Simonsen almost allowed Gray in on 27 but the former Blade's attempt lacked power.
With seven to play of the first half, Bobby Hassell was booked by Mr Salisbury for a foul on Slew. The resulting free-kick was whipped in by Williamson and headed home by Matt Lowton from a few yards.
United had a shot blocked from Williamson as the home side and crowd salvaged some belief from the equaliser.
With seconds of the first-half to play, the Blades' goalscorer Lowton danced into the area before unleashing an effort that was always rising.
In the two minutes of added time, Butterfield was cautioned for a late hack at Williamson down the United right.
A 25-yard strike from Mellis was the first attempt after the break but the Chelsea loanee's effort was always rising.
Lowton was the man of the moment for the Blades and saw another effort blocked by a sea of Barnsley defenders on 51 minutes.
Former Sheffield United man Mellis was replaced in midfield by Reuben Noble-Lazarus on 53 minutes.
A minute before the hour and Luke Steele failed to handle what looked like a tame effort from Williamson, but the former Man United stopper couldn't hold on and it squirmed over the line.
The next eight minutes saw little action from both sides, as both managers pondered potential changes to formations and personnel.
Montgomery found his name in the book for a late foul on Matt Hill. Jordan Clark then replaced Bobby Hassell in a bid to bolster the attacking midfield. Clark was booked barely a minute later for apparently bringing a United man down.
On 82 minutes the Reds had a great chance from a 20-yard free-kick after Butterfield was brought down. Trippier's strike was expertly despatched but met by a wonderful save from Simonsen.
It was all square on 84 mintues as Danny Haynes bagged a brace. Matt Hill's delightful delivery found the head of Haynes from 10 yards who nodded home in front of the travelling Red Army.
Five minutes were added and Ched Evans left the field on a stretcher after landing awkwardly.
It was tight and tense throughout but a point apiece was probably fair as both United and the Reds had spells of dominance in the South Yorkshire derby.
Sheff Utd: Simonsen, Montgomery ©, Henderson, Williamson, Mattock (Cresswell 90), Lowry, Quinn, Lowton, Slew (Evans 71), Helge Riise (McAllister 71), Maguire.
Subs: Doyle, Aksalu, Kozluk, Collins.
Barnsley: Steele, Hassell, Shackell ©, Doyle, Foster, Haynes, Trippier, Mellis (Noble Lazarus 53), Butterfield, Gray, Hill.
Subs: McEveley, O'Brien, Preece, Arismendi, Rose.
Referee: G. Salisbury
Assistants: B. Roberts & P. C. Wright
Fourth Official: D. I. Storrie