On September 16, the City of Chicago issued the last of three phase permits for 400 S. LaSalle St., the longtime home of the Cboe options exchange at the south end of the Loop. The permit covers "interior alterations to existing 7-story office building to convert to a data center," including new equipment and upgraded mechanical, electrical and plumbing systems. Its reported value is $151.1 million, the third-largest building permit across the 51 cities Morningline tracked this fall.
The building where traders once worked the options pits is being rebuilt to house computers.
Seven months of permits
The city's records show the conversion arriving in stages:
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- January: a permit for interior demolition of office partitions on the 1st and 4th through 7th floors, reported at $3.8 million.
- April: work on the lower-level ComEd vault room, the building's connection to the utility grid.
- July 1: Phase 1, demolition from the basement through the 7th floor and in the mechanical penthouse, reported at $4.0 million.
- July 6: Phase 2, "infrastructure upgrades" to "convert 7 story office building to a data center," reported at $51.1 million. The permit calls for reinforcing the existing floors and running power from the ComEd vault to the upper floors.
- July: a temporary construction hoist and six sections of scaffolding up to 122 feet tall on the building's east and west sides.
- September 16: Phase 3, the equipment and building systems, at $151.1 million.
The three phase permits add up to $206.2 million in reported value. Counting the earlier demolition and vault permits, the address has drawn $210.3 million in building permits since January. Permit values are estimates filed with the city, not contract totals. Bloomberg reported the full conversion at $300 million to $400 million.
From trading floors to computer floors
The building sat empty after Cboe moved its headquarters a short walk away to the Old Post Office. In 2024, the developers Prime Group and Capri Investment Group bought it for $12 million. In late October 2025 they sold it for $40 million to a venture of Legacy Investing, a Virginia-based real estate firm, the Chicago Sun-Times reported. The price more than tripled in about a year, and power was the reason: Bloomberg reported that the sellers had secured more electricity for the building from Commonwealth Edison.
Legacy and its partner GI Partners plan a 33-megawatt data center in the building's 300,500 square feet, Data Center Dynamics reported. Legacy hopes to add another 17 megawatts if ComEd can supply it, according to Bloomberg. According to Bloomberg, the building suits the job for the same reasons it suited an exchange: high ceilings, deep wiring and trading floors with no columns in the way.
"From trading floors to computer floors!" Legacy wrote when it announced the deal, saying the facility would be ready for service in 2026. Data Center Dynamics reported that the building can deliver more than 20 megawatts by early 2027.
One detail differs between the records and the coverage. News reports describe a six-story building, while the city permits describe a seven-story office building with work on the 1st through 7th floors.
Not the only Loop office going this way
Other Loop owners are weighing the same move. In August, the city's landmarks Permit Review Committee approved an initial plan to convert floors two through six of 300 W. Adams St., a landmarked 1927 office building, into a data center with a ComEd vault and ten rooftop backup generators, the Sun-Times reported. Preservation Chicago called it "a dangerous precedent." The full landmarks commission still has to vote.
The demand behind these deals is large. The Chicago area absorbed 368 megawatts of data center capacity in the first half of 2025, according to figures cited by the Sun-Times.
How we count
Permits come from the City of Chicago's building permit records for 400 S. LaSalle St., issued January through September 2026. Values are the valuations reported on the permits, not contract amounts. Trade permits are not included in the totals. Company names come from the news coverage linked here.
See all of Chicago's latest permit numbers, updated weekly.
Sources
- Chicago Sun-Times, "Former Cboe headquarters in the Loop sold for $40 million ahead of data center conversion" (Nov. 7, 2025): chicago.suntimes.com
- Bloomberg, "Old Downtown Chicago Trading Hub Is Reborn as an AI Data Center" (2026): bloomberg.com
- Data Center Dynamics, "Legacy Investing & GI Partners announce 33MW data center in Chicago, Illinois": datacenterdynamics.com
- Chicago Sun-Times, "Loop data center pitched for landmarked office building" (Aug. 13, 2026): chicago.suntimes.com
- Real Estate Journals, "Cboe puts headquarters on the market ahead of move to Old Post Office": rejournals.com
- City of Chicago building permits 101077548, 101080339, 101083036, 101081181, 101082470, B200478464 and 101084518.
- Photo: Warren LeMay from Covington, KY, United States, CC BY-SA 2.0, via Wikimedia Commons: commons.wikimedia.org
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