A gigawatt-scale data center has been proposed at a former steel mill in southern Illinois.

Alton Steel updated its website this week with a link to a dedicated project website for the Riverbend Technology Center, a proposed data center project at the company’s former steel mill at 5 Cut Street.

Alton is a city on the Mississippi River in Madison County, about 18 miles (28.9km) north of St. Louis, Missouri.

TerraWatt is proposing turning the 381-acre site in Alton into a data center. The grid-connected project would total up to 1GW, developed in 200MW blocks.

“We know every community is unique. Our proposal for Alton puts the mill site back to work for the economy of the next century,” said David Daneshforooz, co-founder and chief executive officer of TerraWatt. “We’d pay our own way with no local tax incentives, generate millions of dollars a year in new tax revenue for the city and its schools, and be the quietest neighbor Alton has had on this site in a hundred years.”

TerraWatt has a contingent agreement to buy the site from Alton Steel Inc. The sale would close in 2027 only after a use determination and rezoning approval by the City of Alton, Ameren Illinois’ study of the site, and TerraWatt’s due diligence.

If approved by Alton city officials, demolition and site work would begin in 2027, with construction of the first block running from late 2027 into early 2029. The campus could be fully operational by 2031.

“TerraWatt would clear the mill buildings, pay for the cleanup, and build a data center in their place,” the website said. TerraWatt said it would pay for any upgrades to the local grid. The site could use a closed-loop cooling system.

TerraWatt said it is in discussions and hasn’t signed any lease for the site’s capacity.

In operation for nearly 100 years, the Alton mill was once operated by Laclede Steel, a steel manufacturer founded in 1911. The company went bankrupt twice, in 1998 and 2001. After a couple of idle years following the second bankruptcy, the site was sold for $1 million through a federal and state settlement and saw the establishment of Alton Steel to run operations. In 2019, Alton Steel employees took possession of the company through an employee stock ownership plan. The mill closed again in January 2026. The site currently reportedly totals 1.26 million square feet of mill, plus numerous scrap and slag piles.

“Closing Alton Steel was an extraordinarily difficult decision, particularly given the employees and families whose livelihoods were connected to this mill,” said CEO Chris Ervin in a statement. “Our responsibility now is to manage the company’s remaining obligations and secure the best possible outcome for our creditors. This proposed sale represents a significant opportunity to do that while giving the property a productive future.”

TerraWatt is a recently formed data center developer claiming a pipeline totaling 4.5GW, spanning 3,165 acres and eight markets. The company says it is expected to deliver 495MW across four markets by 2017.

TerraWatt is also looking to develop a 120MW facility in St. Louis in an old warehouse, known as the Amory Innovation Data Center. TerraWatt is currently suing St. Louis over conditions placed on the development by local officials. The company hopes the project can be operational by late 2028.