Chalk AI has grabbed roughly 26,600 square feet at 43 West 23rd Street in Manhattan’s Flatiron District, a lease that tops off the eight-story Class B office building at full occupancy. The deal is the latest sign that artificial intelligence companies are still bulking up their footprints in Midtown South as they scale up teams and infrastructure.
The lease covers about 26,607 square feet and was arranged by landlord broker Okada & Company, with asking rent reported at roughly $85 per square foot, according to Commercial Observer. Venture Commercial’s Jason Majlessi and Arash Sadighi represented Chalk AI in the deal, and Okada said his team was "absolutely thrilled" to welcome the tenant as the signing brought the building back to full occupancy. The length of the lease was not disclosed.
Chalk's New York Push
San Francisco-based Chalk, founded in 2022, lists a prior New York outpost at 54 West 21st Street on its company site. The startup raised a $50 million Series A in May 2025, according to a BusinessWire release that detailed the funding round led by Felicis. That capital has supported hiring and larger office footprints as Chalk moves beyond an initial creative-office setup.
Why Landlords Are Listening
The Chalk signing follows a string of sizable Manhattan leases this spring and underscores a tighter market in Midtown South, with a rebound in leasing that helped jolt the Manhattan market back to life. Brokers told Commercial Observer they have seen a more than 200 percent jump in square-footage requests from AI tenants compared with last summer. For owners of renovated Class B product in well-connected blocks, that demand is translating into fewer vacancies.
Property records indicate Castro Properties has owned 43 West 23rd Street since the early 1970s, and the building's new status removes a rare block of available creative office in Flatiron, per PropertyShark. Local business reporting first highlighted the Chalk lease in Crain's New York Business, and neither the tenant nor the landlord has announced an immediate move-in timetable.
