As soon as the Sonoma-Marin Area Rail Transit (SMART) train doors slid shut and it edged away from the station during preview rides on Thursday, a giant cheer rose up from the crowd packed in the train car's seats and aisles.

"This is historic," said Tony Brown from Sausalito, as the car moved down the tracks, blowing its train whistle.

Thursday's soft opening of SMART marked the first public opportunity to ride the long-awaited train connecting Sonoma and Marin counties. In 2008, voters approved a quarter-cent sales tax to fund the train. And after many delays, people are understandably curious to see what they've finally gotten. Hundreds of train enthusiasts, prospective commuters and residents came out for the free round-trip rides between Rohnert Park and San Rafael. The free preview rides continue on Saturday, July 1, and Tuesday, July 4.

Officials had previously aimed for “late spring 2017” as a launch date for the train, after a design flaw delayed the 2016 launch and a downturn in the economy left the agency with insufficient funds to hit the original 2014 launch date.

Now it's finally here -- though only in preview mode.

Some passengers wore conductor hats or train-themed shirts; many of them are hobbyists or historians. "I'm a train buff," said Brown. "I love trains, and to have one coming to Marin County? I had to be here."

Indeed, the round-trip ride between Rohnert Park and San Rafael was marked with old-fashioned hallmarks of train travel. Scenic vistas scrolled past, offering views of wooden barns in Penngrove, old boats in Petaluma and wide-open marshland near San Rafael. Strangers struck up conversations: Two Deadheads discussed Olompali State Park as we passed it. Sports fans debated the NFL draft.

The ride was smooth, if a little hot. One nun taking the trip in full wardrobe took pictures with her phone. Children sat cross-legged on the floor and played games.

It was his children, said Micah Carlin-Goldberg of Petaluma, that brought him out for Thursday's ride.

"They're train-crazy," said the schoolteacher. "All three of them. Their favorite thing to do on the way home from school is to go by the train tracks to see the train."

A conductor estimated the ridership was at its maximum capacity of 300. While those riders seemed to anticipate full service soon along the 43 miles between the Sonoma County Airport and downtown San Rafael, an official opening date has still not been announced.

"We hope it helps relieve the traffic," said Curtis Finley, from Marin City. "And this is great for recreation. I would love to bring bikes and explore Sonoma County."

Finley echoed a common sentiment among some in the North Bay: that it was "a fatal error" to reject BART service to Marin County in the 1970s. The SMART train, he hoped, will begin to make up for the oversight.

When the train does ultimately launch regular service, it will stop at 10 stations between Santa Rosa and San Rafael during this first phase. One-way fares will cost between $3.50 and $11.50, with senior and youth discounts. Subsequent phases are scheduled to include service next to Larkspur, where riders will be able to connect to ferry service, and eventually north to Cloverdale.

Aubri Lane and Caroline Rausch of Santa Rosa had been "looking forward to this for years," said Rausch, and had already made plans for recreational outings on the train.

"And not to take the car!" added Rausch. "Did you see all those cars on the freeway? Oh my God, just sitting there!"

Standing on the Rohnert Park platform after the ride, Lane singled out the scenery as a highlight. "Between Petaluma and Novato, you can see all the wetlands. It's gorgeous. Herons, egrets, starlings, jackrabbits, ducks. Everyone should try it."