Capital Concentration: Downtown San Francisco and the Physical Footprint of the AI Boom
Published March 16, 2026
By Annoushqa Bobde, DSFP Research & Data Analyst
For two years, downtown San Francisco's office market has been defined by "return to office" headlines featuring outsized leases from AI's biggest names, OpenAI and Anthropic chief among them.
Underneath the marquee deals is a broader pattern: a wide base of smaller companies, many just two or three years past their first funding round, independently signing bigger leases as they grow. This distinction matters for how downtown's recovery should be read. A market propped up by a few giant anchor tenants depends entirely on those companies staying large, staying in San Francisco, and staying in growth mode. A market where dozens of smaller, funded companies are signing bigger leases on their own timelines has real depth: demand spread across a cohort of companies at different stages rather than concentrated in a handful of balance sheets.
To understand where that depth is coming from, we analyzed the SEC's Form D filings for Q1 2026, filtered for San Francisco. Form D captures where private capital is landing today, often months before that capital shows up as a signed lease. Mapped by address, the filings reveal a clear geographic concentration. Downtown San Francisco isn't just benefiting from the AI boom. The data suggests it's becoming one of the boom's clearest physical centers of gravity, the place where a critical mass of funded companies is registered, growing, and increasingly putting down roots.
What follows: the map of Q1 2026 private capital funding, the analysis behind it, and the leasing and investment activity already taking shape in many of the same neighborhoods the funding data highlights, with downtown San Francisco leading the way.
What follows: the map of Q1 2026 private capital funding, the analysis behind it, and the leasing and investment activity already taking shape in many of the same neighborhoods the funding data highlights, with downtown San Francisco leading the way.
A Map of Where the Capital is Concentrating
Before looking at any single lease or building, the funding map itself makes a case. It shows, block by block, where the money fueling this generation of AI and tech companies is actually registered. A dense cluster of well-capitalized companies in one place is a meaningful signal on its own, distinct from any one project or lease. It's a picture of where the next wave of hiring, growth, and office demand is most likely to originate, and right now, that picture points strongly downtown.
This map plots each qualifying San Francisco filing at its registered address, with bar height scaled to total amount sold rather than filing count. A single address where one company closed a large round outweighs a cluster of smaller, unrelated filings nearby.
The tallest bars cluster in the downtown core: the Financial District and its immediate surroundings, with a clear secondary cluster near Jackson Square and the Embarcadero corridor. Because Form D reflects the address listed in the filing, the map should be read as a geography of registered fundraising activity, giving a strong read on where capital and company headquarters are concentrating even before every company's day-to-day footprint fully catches up.
Methodology
Why Form D
Most public reporting on startup funding comes from press coverage of individual rounds, TechCrunch write-ups, or aggregator databases that rely on companies choosing to disclose. That reporting is directional but incomplete: plenty of companies raise money quietly with no press release, and funding databases often lag by weeks or months, waiting on self-reported data.
Form D is the notice filing companies submit when raising capital through many exempt securities offerings, including most of the venture financing market, from seed rounds to late-stage growth rounds.
Building the Dataset
The SEC doesn't publish Form D as a single clean file. It publishes the pieces separately: who filed, what the deal terms were, and when. Building the dataset meant joining those pieces into one table, where each row represents a single company's single funding round, complete with address, dollar figures, and filing date.
Two decisions shaped the analysis more than anything else. The first was narrowing the dataset to companies with a San Francisco address. The second was the removal of venture capital funds, hedge funds, and other pooled investment vehicles entirely. Those funds file Form D too, but a fund's filing represents capital flowing into the fund manager's next investment vehicle, an entity that doesn't lease office space, rather than into an operating company. Stripping those out isolates the right population for this analysis: operating companies raising money to grow.
Finally, all filings were sorted by investment field. Some filings disclose the amount sold, capital that has verifiably changed hands. Others disclose only a target offering amount with no confirmed close, which still signals fundraising activity in motion. The map focuses on the amount sold: filings where money has been confirmed to have moved.
Money Precedes Footprint
Funding doesn't guarantee a lease, but it tends to increase a company's capital, hiring plans, and confidence to expand its physical space over time. Several recent examples show how that has played out. Rad AI announced it raised $60 million in January 2025 and, despite initially prioritizing remote work, signed for 11,500 square feet in May 2026 on the 25th floor of 55 2nd Street, up from the roughly 3,000-square-foot office it previously occupied. Hex announced it raised $70 million in May 2025 and more than doubled its San Francisco footprint in March 2026, moving from 8,500 square feet into a 20,000-square-foot lease on the 10th floor of 100 Montgomery Street. Both cases took roughly a year to unfold, a reminder that leasing decisions move on a slower timeline than fundraising does, and that the Q1 2026 cohort mapped above is likely still early in that process.
The map captures where operating-company capital is concentrated right now, in the first quarter of 2026, largely before it has translated into signed square footage. Read alongside the historical pattern, it's an early marker of where the AI boom is planting itself, positioning downtown as a hub for innovation and tech, not just a beneficiary of it.
From Filings to Floors
Tech and AI companies leased more than 14 million square feet across San Francisco and Silicon Valley in 2025, 55 percent of total leasing activity, according to CBRE. The Real Deal put San Francisco's first-quarter net absorption at 1.6 million square feet, with AI companies driving nearly 40 percent of deal volume, the city's strongest post-pandemic quarter.
Behind those numbers is a specific, repeated behavior: funded companies are translating capital into larger office commitments. As Newmark's Mo Spikes told the SF Business Times, venture funding has long been one of the strongest drivers of tenant demand in San Francisco's tech-heavy market. Companies that once took small, short-term spaces to get through their first raises are now moving into leases sized for their next stage of growth.
One Market Plaza offers one of the clearest showcases of that behavior. Assort Health, an AI healthcare company, took three floors there in a deal that more than doubled its San Francisco footprint. Three more leases were announced in the same building in late June 2026, and according to Elecor Properties, about 150,000 square feet have been signed at One Market Plaza since the start of 2026. Disney Streaming Services LLC is reportedly nearing its own deal in the building. Rad AI's lease at 55 Second Street reflects the same pattern on a smaller scale.
The rebound extends beyond AI. Pacific Workplaces' 30,000-square-foot lease at 315 Montgomery, Happen Bank's new headquarters at 88 Kearny Street, and the San Francisco Chronicle's relocation to 450 Sansome point to renewed confidence from flexible workspace operators, financial institutions, and media tenants alike.
Vacancy data adds a sub-district signal. Some of the steepest year-over-year vacancy drops, according to JLL and the SF Standard, occurred just outside the downtown core, including Jackson Square, which landed its own signature deal in April 2026 when consumer electronics company Nothing signed for space there. The rebound isn't confined to large downtown towers. It's spreading into adjacent submarkets where vacancy is tightening, and new tenants are making visible commitments.
Putting Money Where the Momentum Is
Existing property owners appear to be taking cues from the leasing rebound, reinvesting because they have confidence in where the market is headed. This lines up with a broader race to quality: the submarkets with the lowest vacancy and strongest absorption, the Financial District, Jackson Square, and the blocks around them, are also where landlords are putting in capital.
One Market and One Front are in the middle of multimillion-dollar renovations backed by Elecor and Rithm Capital. Separately, investments in shared amenity spaces, including The Cove at 525 Market Street, point to the continued race to quality across downtown buildings.
The ownership market is also shifting. Since April 2026, Presidio Bay has purchased the former home of the Federal Reserve Bank of San Francisco, 301 Battery Street; Lone Star Funds and Harvest Properties have entered a partnership for 600 California St; and Flynn Properties has entered talks to acquire 225 Bush Street through a debt-backed deal.
Conclusion
Three signals point to the same place. Form D filings show where operating-company private capital is concentrated today, ahead of many leases being signed. Leasing activity in Q2 2026 shows capital converting into square footage in many of the same buildings and submarkets that the funding map already flagged. And reinvestment data, from tower renovations to ownership changes at 301 Battery, 600 California, and 225 Bush, show landlords underwriting that same recovery with their own capital.
Together, these signals describe a market with real depth: demand spread across a wide base of companies at different stages, concentrated downtown, and reinforced by the people who have the most at stake in getting the read right. The capital data points to downtown San Francisco as one of the AI boom's clearest physical footholds.
