California officials will break ground Tuesday on one of the largest infrastructure projects in state history, a massive high-speed rail line that will connect the state’s two largest metropolitan areas.

The rail project, estimated to cost $68 billion over the next 14 years, will initially connect Los Angeles and San Francisco. When it’s completed, it will allow passengers to travel between the two cities in less than three hours, at top speeds of more than 200 miles per hour.

Gov. Jerry Brown (D) will be on hand Tuesday when officials hold a groundbreaking ceremony in Fresno, where the first 29-mile segment of the rail line will begin construction. As Brown begins his fourth and final term in office, the rail line represents a major part of the legacy Brown hopes to leave behind.

“We should be able to have at least one high-speed rail, and the only place that’s going to happen in our lifetime is California,” Brown told The Washington Post in an interview last year. “That’s an important component of an integrated transportation system.”

Phase one of the project is planned to run from Anaheim north through Burbank, Palmdale, Bakersfield and Fresno, then west to Gilroy, San Jose and into San Francisco. A longer-term phase two will connect the main line with Merced, Modesto, Stockton and Sacramento in the north, and Riverside, Escondido and San Diego in the south. Once both phases are complete, the system will cover 800 miles through 24 stations.

The groundbreaking “really marks the transition from all the planning and appropriations and legal challenges and the design work to continuous construction,” said Dan Richard, chairman of the California High-Speed Rail Authority, the project’s governing body. “It’s a significant milestone.”

But the project is not without controversy. Local governments and opponents critical of the rail system’s cost and legality have sued to block the project several times. Those suits, along with slower-than-expected land acquisition, have set back the beginning of construction by two years.

The California Supreme Court ruled in October against a suit brought by Kings County that would have blocked construction. The federal Surface Transportation Board ruled in December that construction did not have to comply with the California Environmental Quality Act, removing another hurdle to construction.

Other local governments, including Bakersfield, Shafter and Kern County, have reached settlements with the rail authority.

Even with the legal and political victories, the funding structure is incomplete. Voters approved a $9.95 billion bond aimed at funding the initial construction of the rail project in 2008, by a slim five-point margin. The Obama administration added another $3.2 billion in federal grants, and the legislature agreed in 2014 to provide funding through cap-and-trade taxes on greenhouse gases, which will add another $250 million to $1 billion per year.

Still, that means the rail authority will have about $26 billion at best, less than half the estimated total costs. California High-Speed Rail Authority officials have said they expect advertising, real estate developments and private investors to fund up to a third of the total costs.

And as with most major infrastructure projects, costs are likely to rise as new hurdles emerge. Last year, the rail authority boosted its cost estimate for one key segment in the Central Valley by 15 percent, or about $1 billion. Some opponents believe the costs could skyrocket to about $250 billion or more.

“It’s becoming increasingly clear now that the project remains wholly unviable. The financing, the performance parameters, the ridership assumptions are all way off,” said Jon Coupal, president of the conservative Howard Jarvis Taxpayers Association. “This is a monumental waste of valuable transportation dollars.”

Richard credited Brown for maintaining a steady vision for the project, even as some of its supporters began to question its value. “The one constant through all this is that the governor, Jerry Brown, decided this was going to be something that was going to be important for the future of California. He’s been steadfast,” Richard said.

But challenges lie ahead. Coupal said Republican control of Congress makes it unlikely California can rely on any additional federal funding, which was initially supposed to account for a third of the total costs.

One of the top GOP leaders standing in the way of further federal funding is House Majority Leader Kevin McCarthy (R-Calif.), whose district includes Bakersfield, a midway point on the line between San Francisco and Los Angeles. McCarthy has vowed repeatedly not to allow any additional appropriations.

“After the Obama Administration’s unaccountable spending in the early years of his presidency, the American people spoke loudly and ushered in a new Republican Congress to stop the waste. As a result, my colleagues and I decided that no federal money would be spent on such a wasteful project,” McCarthy said in a statement to be released marking the groundbreaking. “Congress will continue to ensure no more Federal taxpayer dollars are directed to this project.”

Richard, chairman of the rail authority, said his agency doesn’t expect federal funding in the next four to five years. He pointed to Japan, where nearly a third of funding for high-speed rail projects comes from real estate development near rail stations.

“We do not need to rely on any further federal funding at this point, but I do think in the future, we’ll be able to make a case,” he said. “We’re going to have a tremendous level of transparency, and I think we’ve put in place the strongest governance and oversight system of any project I’ve ever seen.”