Nearly $2 billion in federal money needed to build the long-awaited Red Line extension to Chicago's southern border was promised in writing on Friday, ensuring the grant can't be taken back by incoming President-elect Donald Trump.Chicago Transit Authority President Dorval Carter Jr. heralded the funding agreement as the last critical step to begin construction this year of the $5.7 billion rail extension to 130th Street.Carter said the agreement fulfills a promise made by politicians more than 50 years ago to extend the CTA's rail system — and reverse years of transit discrimination against the Far South Side."This is about much more than extension of a rail line," Carter said at a news conference Friday, flanked by Mayor Brandon Johnson and a handful of U.S. legislators at House of Hope Church, 752 E. 114th St. "It's about the future on the Far South Side of Chicago. And it is one of the biggest, boldest equity investments in the history of this great city," Carter said. U.S. Rep. Robin Kelly, U.S. Sen. Dick Durbin and Federal Transit Administration Deputy Administration Veronica Vanterpool attended a news conference Friday about the Red Line Extension Project.Pat Nabong/Sun-Times The project, estimated to be completed in five years, includes four new stations at 103rd, 111th, 116th and 130th streets. Tracks will be elevated from 95th Street to 118th Street, where they will move to ground level, according to the CTA.The Federal Transit Administration first promised the $1.97 billion grant in 2023. But Carter said the "unique legal document" signed Friday with Federal Transit Administration Deputy Administrator Veronica Vanterpool ensures the money cannot be clawed back by a new presidential administration."Historically, there's never been a situation in which a full funding grant agreement has been reneged by the federal government," Carter said. Federal Transit Administration Deputy Administrator Veronica Vanterpool on Friday signed a full funding grant agreement for the Red Line Extension Project at the House of Hope in the Pullman neighborhood.Pat Nabong/Sun-Times U.S. Sen. Dick Durbin suggested that, without the signed agreement, funding could be imperiled by Trump, who is set to take office on Jan. 20 and might target the Democratic city."You never know about change," Durbin said. "That's why we're meeting today. Whatever the change may be, the Red Line will finally be finished."Carter unveiled a mock-up of a new CTA map including the planned Red Line extension. He said the maps would be distributed soon. Chicago Transit Authority Carter said he does not anticipate the project's cost to increase further over the five years of anticipated construction. Design and construction contracts have already been doled out, he said. The CTA last year increased the project's budget twice, from $3.6 billion to $5.75 billion.Carter said the entire project could have cost significantly less if it was completed when it was first promised by politicians after the 95th Street terminal was opened in 1969."Do you know how much it would have cost if we had built this project back when we built the Red Line? ... $144 million. So think about the cost of time," Carter said. The CTA 95th Red Line stationTyler Pasciak LaRiviere/Sun-Times file