Data Platform Chalk Grabs 27K SF in Flatiron District
By Isabelle Durso July 23, 2026 11:30 am
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Another artificial intelligence firm is planting roots in Midtown South.
Chalk, a data platform that provides companies with infrastructure to deliver data to AI agents, has signed a lease for 26,607 square feet at Castro Properties’ 43 West 23rd Street in the Flatiron District, according to landlord broker Okada & Company. Asking rent was $85 per square foot.
The deal represents Chalk’s second Flatiron office location after it opened its first office at 54 West 21st Street four years ago.
The AI firm’s new lease also brings the eight-story office building one block west of the landmark Flatiron Building to 100 percent leased, according to Okada, as more and more AI and tech firms look to Midtown South for their offices.
“We are absolutely thrilled to welcome Chalk to 43 West 23rd Street and to bring the property back to 100 percent occupancy,” Okada’s Christopher Okada, who represented the landlord in the deal, said in a statement. “Our firm has seen an increase of more than 200 percent in the square-footage requirements submitted by AI tenants compared with last summer. These companies are predominantly targeting well-located, renovated Class B office buildings throughout Midtown South.”
The length of the lease was not disclosed. Venture Commercial’s Jason Majlessi and Arash Sadighi represented the tenant.
“43 West 23rd Street and the ownership provided the opportunity for Chalk to meaningfully expand in New York City while maintaining the flexibility high-growth AI companies need out of their real estate,” Majlessi said in a statement to Commercial Observer.
Spokespeople for Chalk and Castro Properties did not immediately respond to requests for comment.
Castro Properties, run by the Castro family, has owned 43 West 23rd Street since 1972. It’s unclear when Chalk will move into the property.
San Francisco-based Chalk was founded by Marc Freed-Finnegan, Elliot Marx and Andy Moreland in 2022. Last year, the company raised a $50 million Series A funding round at a reported $500 million valuation.
Isabelle Durso can be reached at idurso@commercialobserver.com.
