MILLBRAE — A parade of politicians attended a groundbreaking ceremony for Caltrain’s electrification project on Friday, heralding the start of what they called the most important upgrade in the rail line’s 153-year-history.

The $2 billion project — delayed after the Trump administration held up a key federal grant before putting it back on track in May — will mean faster, greener and more reliable service, replacing the current diesel trains that go back and forth between San Francisco and San Jose’s Tamien station with a new fleet of electric train cars.

Elected officials on the Millbrae station’s southbound platform turned over some dirt with gold-painted shovels Friday morning to cheers and applause, but work on the project actually began behind the scenes in June.

In Salt Lake City, a contractor has started designing the new electric trains, with components to be assembled around the country. And back home engineers are planning work on tracks and overhead power lines, purchasing necessary land along the corridor and finding ways to fit in the electric transformers that will power the new trains.

When the first electrified Caltrain trips start running — a milestone expected in 2021 — they’ll be able to handle 80 percent more passenger trips a day than they do now.

On Friday, Gov. Jerry Brown, House Minority Leader Nancy Pelosi, D-San Francisco, and elected officials from up and down the Peninsula took a victory lap over one of California’s first showdowns with the Trump administration.

Before Trump took office, a $647 million federal grant for electrification had been all but approved by the federal Department of Transportation. But amid opposition from California’s Republican congressional delegation, whose members argued that the electrification project would boost the state’s high-speed rail project, incoming Transportation Secretary Elaine Chao decided to hold up the grant approval.

Chao finally released the grant after California officials made a full-court lobbying effort, with U.S. Sen. Dianne Feinstein refusing to support nominees to Chao’s department until she approved the project.

The Trump administration changed course because “we were gum stuck to everyone’s shoe,” said Rep. Anna Eshoo, D-Palo Alto. “We were not going away.”

Brown credited the state’s congressional delegation with using “some magic” to push “this through the Trump administration,” as he waxed nostalgic about riding the Daylight train to Palm Springs with his mother as a kid in the 1940s.

The speeches were interrupted by service announcements about BART and Caltrain, as surprised straphangers stared out the windows of passing trains at the crowd. Balloons hovered overhead at the event, which had a celebratory air.

Speakers focused on the long-term impacts that the electrification project would have on the Bay Area. “If we don’t do this and we don’t expand the capacity of our public transit systems in the Bay Area, we will have another million cars on the road,” said state Sen. Scott Wiener, D-San Francisco.

The project is expected to remove 619,000 vehicle miles a day and 176 metric tons of CO2 emissions a year from the region.

Others talked about Caltrain’s history — the days when the train tracks were a stagecoach road and the journey between San Jose and San Francisco look nine hours.

“On bad days, it’s not that much better today,” joked Carl Guardino, the CEO of the Silicon Valley Leadership Group.

Electrified service will be faster because electric trains are quicker to start and stop than diesel trains. The old diesel trains will be decommissioned, officials say.

But electrification is just the first stop in Caltrain’s future. The electrified line will also be a key part of the state’s high-speed rail system, which should eventually stretch from Los Angeles to San Francisco and run along the Caltrain tracks from San Francisco to San Jose.

The electrification is expected to be finished long before any high-speed trains run here, and that project will require station expansions. Bullet train stops are expected at San Jose’s Diridon Station, Millbrae and the new Transbay Transit Center in downtown San Francisco.

Officials have yet to decide whether they will build new elevated tracks to give high-speed trains their own right-of-way, or add in passing tracks to let the bullet trains whiz by Caltrain cars, said Seamus Murphy, a Caltrain spokesman.

Caltrain passengers waiting for the train at the Millbrae station on Friday said they were excited about the prospect of faster service.

“The more we can get connected, the better,” said Ashley Howitt, 50, who was on her way from San Francisco to Santa Clara. “How great will it be to get all those people out of their cars?”