The funding consists of a $100 million award for pre-construction work and a $650 million multiyear commitment, part of nearly $1.3 billion in transportation grants announced by Governor Gavin Newsom on November 10 through the California State Transportation Agency's Transit and Intercity Rail Capital Program. The program distributed funds across 19 projects statewide.

The state money is intended to help leverage a $3.38 billion federal contribution proposed in 2024 through the Federal Transit Administration's Capital Investment Grants program. But the Transbay Joint Powers Authority, the agency overseeing the project, has not yet secured a Full Funding Grant Agreement from the FTA, leaving the federal commitment unconfirmed.

The Portal would extend Caltrain 2.2 miles from its current terminus at Fourth and King streets to the Salesforce Transit Center, which was built with an underground train station but currently serves only buses. The project includes a tunnel, a new station at Fourth and Townsend streets, and completion of the transit center's underground train box with six tracks and three center platforms. Trains would enter the tunnel near Fourth and King and arrive two levels beneath the street at the transit center.

The same infrastructure is designed to eventually accommodate California high-speed rail trains, should that project be completed.

The extension was first proposed in 2014, while the Transbay Transit Center was still under construction, with the goal of transforming the facility from a bus terminal into a regional rail hub. But funding uncertainty, cost overruns, and delays have repeatedly pushed the project back. In 2016, the estimated completion date was already being pushed to 2026 at the earliest. By 2024, the project was estimated to cost $6.7 billion, up from $5 billion in 2016. The latest estimate has climbed to approximately $7.57 billion, though the authority's retained budget is $8.26 billion. The current schedule targets construction readiness in 2029 and passenger service in December 2036.

Other Bay Area projects also received funding through the state program. BART was awarded $25 million toward transforming the west parking lot of Berkeley's Ashby Station into a mixed-use development with 618 homes, including 307 affordable units, along with a new parking garage with electric vehicle charging. Planned station improvements include protected bike lanes, wider sidewalks, a public plaza, and electrical upgrades to support more reliable BART service.

Marin Transit will receive nearly $25 million for an electric-bus facility and 11 battery-electric buses, while SMART will receive $2 million for pedestrian safety improvements in Sonoma County. The state is also awarding $30 million to add a second mainline track through Newark and Fremont, helping increase capacity for Altamont Corridor Express trains between Stockton and San Jose. Santa Cruz Metro is receiving nearly $29 million for a new Watsonville maintenance facility and expanded bikeshare.

Caltrain will also receive $4 million toward a battery-electric train pilot between San Jose and Gilroy, and another $6 million will fund signal, track, and safety improvements. Other awards include funding for Metrolink service in Southern California, COASTER in San Diego County, Capitol Corridor improvements, and electric buses and other transit upgrades in Sacramento, the Central Valley, and Los Angeles-area counties.