TerraWatt has proposed buying Alton Steel's 381-acre Illinois mill site and building a data center campus of up to 1GW there. The developer announced the plan on Oct. 21 for the Riverbend Technology Center at 5 Cut Street in Alton. Alton Steel would sell the
Wide landscape shot of the Alton Steel industrial property from broadcast coverage of the data center proposal. land, TerraWatt would develop and own the campus, and Ameren Illinois would supply power. No tenant for the capacity was disclosed.
TerraWatt would build in 200MW blocks up to a 1GW total, starting where the mill's furnaces and rolling mills stand today. Each block carries an estimated $2.64 billion investment, nearly 5,000 construction jobs and 50 permanent jobs, according to St. Louis Magazine. TerraWatt projects $17.2 million a year in new property tax per block, with $9.9 million to Alton School District 11 and $4.2 million to the city government, about 10 percent of Alton's annual revenue.
The 200MW increment reflects what the grid can absorb. Cecilia Dvorak of Steadfastcity Economic and Community Partners, which advises TerraWatt, said Ameren Illinois should be able to deliver about that much in the near term because the mill drew roughly 160MW. "There's still a little bit of the chicken and egg happening here about what the full buildout would look like," Dvorak said.
TerraWatt says it will not seek local tax incentives or draw on the Riverfront TIF district, although the site sits inside the district, which expires in December 2029, First Alert 4 reported. The whole property paid $98,736 in property tax last year. TerraWatt also estimates a 200MW data center would use about 400,000 gallons of water a year, against 177.7 million gallons drawn by the mill.
"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 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."
No application has reached Alton city hall. TerraWatt says the sale would close in 2027, after a use determination and rezoning by the City of Alton and an Ameren Illinois study of the site. Alton Mayor David Goins said the city will hire an outside consultant to review any formal proposal. TerraWatt holds a community open house on Oct. 27 at The Wedge, 620 E. Broadway.
Alton Steel stopped production in January 2026 after more than a century at the site and is marketing the property as it winds down. "It's not a done deal, but we felt that what they proposed brought the best value to all of our creditors," said chief executive Chris Ervin.
Illinois holds 237 data center facilities tracked by Baxtel, led by Meta with five sites and Microsoft Azure with five. The largest is Microsoft's Chicago Northlake campus at 158MW.
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