Dayton onMain: City gives approval for first large building on former fairgrounds site

onMain, the group redeveloping the old Montgomery County Fairgrounds, wants to create a distinctive, walkable urban environment that will be home to “knowledge economy” jobs where skilled workers and other community members want to gather, live and play.

Developers earlier this week received Dayton Plan Board approval to construct the first building on the fairgrounds property — the Think Dayton office building that the group says will bring something new and different to the Miami Valley region and will set the tone for the rest of the site.

“We are really on the cusp of something special and bringing onMain to life,” said Jamie Green, principal with Planning NEXT, a Columbus-based planning and design firm that helped craft a vision for the property. “This building that we’re talking about — the first one — is really emblematic of the larger vision and mission.”

onMain is a partnership between Premier Health and the University of Dayton to reimagine and revitalize the 38-acre former fairgrounds property in Dayton, near the UD campus and across Main Street from Miami Valley Hospital.

This week, onMain was given the go-ahead by Dayton’s Plan Board to begin initial construction on the first phase of the project, which focuses on roughly one-third of the site, at the southern end, at the intersection of South Main and Stewart streets. Every phase of onMain must receive final plan approval.

The first phase of the project will create a 118,500-square-foot office building, an adjacent outdoor plaza and gathering space, a canal park and retention basin with a perimeter walking trail and other community spaces and amenities. Phase 1 also will install streets, sidewalks, utilities and surface and street parking, with initial infrastructure work expected to begin before July 1.

Surface parking will be constructed on the site in Phase 1, but onMain’s plan for future phases is for new housing, offices or parking garages on those lots, said Tony Kroeger, Dayton’s planning division manager.

The proposed “Think Dayton” office building at 1229 S. Main St. will be five stories tall (though a section of the roof will be six stories) and will house a digital transformation center as the centerpiece of Ohio’s second innovation hub.

onMain and Planning NEXT said the $73 million building will offer offices, labs and collaborative research spaces, adding that tenants may have memberships, instead of traditional leases.

Work on the building is likely to start this fall and could be finished in early 2027, coinciding with the completion of the surrounding landscaping and amenity installations.

Green said the building’s design, materials and placement on the old fairgrounds property will start to create a new urban neighborhood, unlike anything else around. The building has a sloped roof and other details that were designed with Dayton’s aviation history in mind.

Kroeger said a planned development that the city previously approved included suggestions and wording to avoid a “boring building” being constructed on the site, and onMain has strived to meet those expectations.

Kroeger said city staff are glad to see that the footprint of the Think Dayton building is built toward the right-of-way at Main and Stewart and does not have a large grassy setback like other developments, including some on the south side of Stewart Street.

onMain and Planning NEXT say the Think Dayton building will be a gateway landmark into what is being called an innovation district, with a focus on the knowledge economy, based on intellectual capital and cognitive skills, abilities and production.

The Think Dayton building “was always envisioned in the master plan to be the catalytic building that sets the tone, sets the first impression for what is to come,” Green said.

Another key part of Phase 1 includes a new residential building. onMain does not plan to construct the new housing, but says more information about that component of the project and future structures will be shared after details and agreements are finalized. The canal park will be about one acre and will have native plantings, flexible gathering space and a restored water channel.

The public plaza next to the Think Dayton building will support “community interaction, special events and passive recreation,” onMain officials said.

Further north on the fairgrounds site, the historic roundhouse building is being stabilized and restored. Those improvements could be completed this fall.