Prologis is getting ready to file a development application that would overhaul the 20-acre Caltrain railyards at Fourth and King, turning the site into a cluster of high-rises anchored by an 850-foot tower set above a rebuilt rail station. The concept lays out a mixed-use neighborhood that could bring thousands of homes and millions of square feet of offices, retail and public space to the Mission Bay-SoMa waterfront.
What's proposed
The proposal outlines a buildout of up to 8 million square feet, including as many as 2,500 housing units and roughly 4 million square feet of commercial space. The first phase alone would span about 2.5 million square feet and include both planned towers. One tower is slated to climb to about 850 feet, with the train station directly beneath it, and the project team is looking at a construction schedule that could stretch 15 to 20 years. These details were reported by the San Francisco Chronicle.
Where it would go
The site covers the blocks between Fourth and Seventh Streets and King and Townsend Streets, and today serves as Caltrain’s northern terminus and an active maintenance yard. Prologis owns the land underneath, while Caltrain holds a perpetual easement to operate tracks and facilities on the property, a legal setup that will shape how platforms, tracks and buildings are arranged. Those boundaries and the easement are described on the project website and in Caltrain materials: SF Railyards and Caltrain documents.
Timeline and approvals
The application starts the clock on environmental review and the Development Agreement process. According to the Planning Department’s railyards FAQ, environmental review for this project could take up to two years, and development agreements are typically shaped over an extended, phased schedule. Independent coverage has pointed to a Planning Department timeline that could see approvals by 2027, with construction starting the following year. Those steps are described in Planning Department materials and in coverage by The Real Deal and the Planning Department FAQ (SF Planning FAQ).
Market backdrop
Brokers and city officials say the timing reflects a shifting Mission Bay market, where AI and other tech tenants have been quickly expanding their footprints and reshaping leasing patterns along the waterfront. Local data cited in reporting point to elevated lab and office vacancy earlier in the decade, along with the potential for vacancy to tighten once recently signed leases are fully occupied. The market context and tenant activity around Mission Bay were covered by the San Francisco Chronicle.
What’s next
Prologis says it will begin community outreach and work with Caltrain, the Planning Department and the Office of Economic and Workforce Development as the application moves through environmental review and public hearings. Project updates and public events are being posted on the developer’s project site as the city negotiates a formal Development Agreement and public-benefits package: SF Railyards.
