TerraWatt proposes up to 1GW Illinois data center on steel site

TerraWatt has proposed a data center of up to 1 GW at a former steel mill in Alton, Ill., under a contingent agreement to buy the 381-acre site from Alton Steel Inc.

Alton Steel updated its website this week with a link to a project page for the Riverbend Technology Center at 5 Cut Street; Data Center Dynamics first reported the posting. The grid-connected campus would be developed in 200 MW blocks. Alton sits on the Mississippi River in Madison County, about 18 miles north of St. Louis.

TerraWatt said it is in discussions and has not signed any lease for the site's capacity. For allocators, the proposal is a pre-leasing proposition: TerraWatt has no signed lease for the capacity, so demolition and the first 200 MW block would proceed on a timeline no offtake contract yet anchors. The project website says the campus could be fully operational by 2031.

TerraWatt said it would clear the mill buildings and pay for the cleanup, and would pay for any upgrades to the local grid. Co-founder and chief executive David Daneshforooz said the project would take no local tax incentives and generate millions of dollars a year in new tax revenue for the city and its schools. The site could use a closed-loop cooling system, according to the project website.

The mill was in operation for nearly 100 years, was once operated by Laclede Steel and closed again in January 2026. The site currently totals a reported 1.26 million square feet of mill buildings, plus scrap and slag piles.

Closing on the sale is set for 2027, and only after a use determination and rezoning approval by the City of Alton, Ameren Illinois' study of the site and TerraWatt's own due diligence. If Alton officials approve the project, demolition and site work would begin in 2027, with construction of the first block running from late 2027 into early 2029.