Twenty months after its introduction, the MTA’s $27 billion Capital Program has been approved.

Gov. Andrew Cuomo announced Tuesday that the five-year budget plan for 2015 through 2019 is in effect after final approval from the Capital Plan Review Board.

The news marks the largest investment in MTA infrastructure in state history but also the latest passage of a capital program in agency history.

“The MTA is the lifeblood of the New York metropolitan area’s transportation network and we must ensure it has the capacity to meet the travel demands of the next generation and fuel one of the largest economies on the globe,” Cuomo said in a statement.

“By investing in the most robust transportation plan in state history, we are reimagining the MTA and ensuring a safer, more reliable and more resilient public transportation network for tomorrow.”

The plan includes funding for huge expansion projects, including $1 billion to begin Phase 2 of the Second Avenue subway; $695 million for four new Metro-North stations in The Bronx, to connect the railroad to Penn Station, and $2.5 billion for the East Side Access project connecting the Long Island Rail Road to Grand Central Terminal.

“Today marks a major step forward for the MTA, and the people of New York,” said MTA Chairman Tom Prendergast in a statement. “With historic levels of funding through the capital plan, we have the resources and support we need to fulfill the Governor’s mandate to renew, enhance and expand our transportation infrastructure.

After extended negotiations and plenty of back-and-forth between the city and state, Cuomo is ponying up $8.3 billion in the capital program for the state-run agency. Mayor Bill de Blasio will contribute $2.5 billion from city funds.

As big as the budget may seem, advocates say $27 billion over five years doesn’t address all the needs of the MTA, a trillion-dollar asset.

“It took forever and it wasn’t perfect,” said Gene Russianoff, spokesman for the Straphangers Campaign. “Transit is political like everything in our society. There’s no smooth scientific path to a capital program. It’s going to be messy. You have all these legislators who want things and they’re not shy about wanting to get them.”

The program will also fund the rollout of more than 2,340 buses and 1,450 subway cars. About $2.7 billion will be invested in the updating and modernization of track signals and communications.

“It’s hard to express how important this program is to the MTA,” said MTA Board Member Andrew Albert, who says the delayed passage has left the agency in a state of flux.

“It’s incredible not knowing what was going to happen…this really should have been approved a good deal earlier.”