Gretna secured the Second Division title and promotion at the first time of asking after coming back from a goal behind to defeat Alloa Athletic.
Brooks Mileson has paid high wages for success
Morton slumped to a 4-0 defeat at home to Ayr United, which means that Rowan Alexander's side cannot now be caught.
Yet Jamie Stevenson had given Alloa an early lead at Raydale Park.
But Stevie Tosh scored just before the break and added another in the second half to make it two promotions in a row for Gretna and owner Brooks Mileson.
Millionaire Mileson was delighted that his side had become the first in British senior football to win a title this season.
"I'm absolutely ecstatic," he told BBC Sport. "That's back-to-back championships, which is just unreal.
"It just seems to get better and better here and it's just a fabulous part of my life.
"I look at our ground and it's a shell of a non-league club and I think how can we have done what we have done?
"We did not expect it today as we thought Morton would at least get a draw.
"It wasn't our usual flowing football, so it was a strange day."
Gretna now have a 19-point lead over Morton in their first-ever season in Division Two - and also have a Scottish Cup semi-final against Dundee to look forward to.
"The players' minds have been there in the last couple of games as I think they've been trying to avoid injuries," said Mileson.
"But I think, with the experience we have in the team, you'll see a different Gretna at Hampden."
Mileson has dipped into his own fortune to finance signings no other club outwith the Scottish Premier League can match.
"Yes, I've put a lot of money into the club, because we did not have a club," he said.
"But we will get bigger and will rely less and less on Brooks Mileson."
Mileson again backed former Morton striker Alexander to be the manager to take the club to yet higher levels.
"I've said before, the day Rowan Alexander leaves Gretna is the day I leave it," he added.
Gretna: Mathieson, Birch, Nicholls, Tosh, Townsley, Innes (Canning 9) (Jenkins 74), O'Neil, McGuffie, Deuchar, Shields (McQuilken 83), Skelton.
Subs Not Used: Collins, Main.
Goals: Tosh 44, 66.
Alloa: Creer, Bolochoweckjy, Ovenstone, Townsley, Anthony Stevenson, McColligan, James Stevenson, Grant, McLeod (Learmonth 82), Ross Hamilton, Sloan.
Subs Not Used: McGeown, Nicolson, Forest, Ferguson.
Goals: James Stevenson 2.
Ref: C Boyle