Nearly two decades in the making, the Salesforce Transit Center in San Francisco is now open, set to connect thousands of Bay Area residents to the city's downtown area.

Crowds of people waited in line Saturday to see the brand new transportation hub in the heart of the city. In fact, too many people showed up and organizers for the opening party had to limit access due to safety reasons.

Access to new Transbay Terminal entrances were shut off at least 20 minutes due to the number of people.

San Francisco Municipal Transit Agency staff are managing capacity levels, according to a spokesperson. If an area goes over capacity, officials are stopping people from entering until someone leaves.

On Friday, several city and state officials joined members of the Transit Joint Powers Authority in a ribbon cutting, celebrating the spacious and modern center's opening.

"This represents San Francisco at our best. It represents our commitment to transportation, our commitment to environmental sustainability and community develop," San Francisco Mayor London Breed said.

"Our city is growing with both jobs and people, and we need to do a better job of moving everyone around this region, and this transit center will do just that. The transit center goes far beyond a transportation hub. It's a thriving place of economic opportunity," she said.

Stretching four city blocks, the $2.26 billion four-story transit center boasts pop-up retail shops, art displays, shopping, dining and a 5.4-acre rooftop public park.

"This is a representation of what can happen when people work together; public, private, nonprofit, community," House Democratic Leader Nancy Pelosi of San Francisco said.

Pelosi also acknowledged the late Mayor Ed Lee for his part in creating the transit center.

"It's about improving the quality of life, improving the quality of air, it's about the good health of our children, it's about the time we save," she said.

Friday's event was part of the culmination of the first phase of a larger project, eventually set to connect to Caltrain and a future California High Speed Rail via underground railways in the two stories below the transit center.

"As many of you remember, we were in the depths of a recession, and I still remember the day we celebrated our groundbreaking as we welcomed workers back to a job site for many, the first time in years." District 4 Supervisor Jane Kim said of the site's groundbreaking, which took place back in 2010.

"This was a huge project to bring to fruition," she said. "I want to thank our residents for our immense patience over the many years as this neighborhood was ground zero for construction, literally 24-hours a day. And thank you for investing in this neighborhood, choosing this neighborhood to live here and patiently living through the noise, the night construction and all of the traffic."

The next phase of construction, the $4 billion Downtown Extension Project, will connect 1.3 miles of underground rail between the center and the Caltrain station at Fourth and King streets. That project is expected to be completed in 2028.

The Salesforce Transit Center will hold a free block party today starting at noon to celebrate its opening.

On Sunday, the center will begin serving buses with Alameda-Contra Costa Transit, Greyhound, San Mateo County Transit District and Western Contra Costa Transit Authority. Buses with the San Francisco Municipal Transportation Agency already started service at the outside bus plaza in June.