It won them two successive promotions and a Wembley penalty shootout in the League One Play-off Final.
It saw them close in on Championship safety despite operating on arguably the smallest budget in the division.
And it helped them seal their second-tier survival in the final nailbiting days of last season after a three-point deduction imposed by the Football League which would have derailed many clubs.
Spirit. Team spirit.
Rotherham United, under Steve Evans, are famous for it.
The manager and chairman Tony Stewart have agreed their recruitment plans for the summer, with their first signing possibly arriving as early as this week.
And the arrival will be a man who puts the team first. Because Stewart, who made his millions through his ASD Lighting company, takes a dim view of any player who eschews his club’s ethos of togetherness.
“I liken it to salesmen at ASD. Everyone is desperate for a salesman, but you’re not too desperate for the wrong salesman,” he told me.
“You want the salesman but you want the right salesman. It’s the same with football. It’s about doing your preparation.
“What do I mean by preparation? Does he throw a sickie? Is he a fit player? Is he a player who could start tomorrow and play tomorrow? Does the guy want to come to Rotherham? Things like that. How many places has he visited in his career?
“A bit like salesmen, if the guy’s had about 15 jobs he’s passing through.
“I like the culture of bringing players through from League Two, to One to the Championship. They’ve become Rotherham players through and through. And it’s that that I want. I don’t want the passer-by.”
Stewart, with that relentless ambition which has built Rotherham’s success as well as a new stadium and fuels his dream of a Millers side in the Premier League under his stewardship, typically takes matters a step further.
So not just team spirit ...
“There’s no doubt that there’s a win spirit - a win spirit, that’s what I call it - at Rotherham,” he said. “We’re insatiable. We want to win every match.”
He’s canny enough to know you don’t always get what you want, but believes the experiences of the last year - the Millers’ first campaign in the Championship in nearly a decade - will make them a stronger outfit next season.
Twelve months ago, Rotherham had just enjoyed the glory of Wembley, but their victory in the play-off final came at a cost, putting their recruitment three weeks behind the clubs with whom they would go on to do battle over 46 matches.
“I think we’re more prepared now. We’ve had more time to prepare,” he said. “Like the manager, like the directors, I’m looking forward to a good season where we can compete at this level for a second time knowing full well that we have been through it once and knowing what we have to do.
“I think we will be more well armed and more prepared to try to play the best level of football that we can.”
We met up at his company HQ, him bristling with bright-eyed vigour and good nature as he bounced along the corridors of ASD Towers and into his office, having just come off the golf course, where he likes to test himself three times a week.
He may be eligible for his bus pass, but his zest for Rotherham United, challenges and life in general shows no sign of abating.
He talked of seeing an Evans list containing “five or six” names for every position before the pair got down to discussing individual targets, and added: “We have many options. You’d be surprised how many players are available.
“Everyone wants a striker. They’re out there. But we want someone that wants to come to Rotherham. We don’t want people who travel around looking for the top price to be paid. There are some players that do that.
“There are other players who are number two or number three at top sides and don’t get a chance. Well, we give opportunities. When we recruit, these players will have opportunities to play in the first team because we want players coming in and playing for Rotherham not what I call stuck in my wardrobe waiting for the climate to change.
“We’re going to be thrifty. We’re going to pick wisely.
“This time we have an extra month. We have time. A lot of preparation has been put in by the manager and scouts. I’ll probably have many meetings about recruitment because we want to be more careful with regard to what we do in getting players in.
“We understand what we’re up against. We’ve played the majority of teams we’ll be playing next season.”
The signings strategy is the product of two men who are close professionally and personally. Stewart nearly always says ‘yes’ when Evans asks him for something, and that’s because Evans wouldn’t dream of making an ill-thought-out request which might invite a ‘no’.
The manager describes Stewart as his best ever boss and one of his dearest friends. They live within a ten-minute stroll of each other (one minute 30 seconds if Alex Revell has just scored at Wembley and Evans decides to make a dash for it) and speak daily.
Players come and go, but their relationship endures.
One of those who came and has now gone is former captain Craig Morgan.
After nearly three seasons of stellar service, the centre-half who was fiercely proud to lead the Millers said: “It’s important when you are a small club in a big league to stay united and together.
“We might not have had the individuals that some teams have, but you have to be 11 people or 14 from the bench all pulling in the same direction.”
It’s unseen, but such a tangible thing.
Spirit. Team spirit. Win spirit.