State and local leaders gathered just north of New Bedford in Freetown to celebrate the start of construction on the first phase of the South Coast Rail expansion project.

Gov. Charlie Baker, Lt. Gov. Karyn Polito, Secretary of Transportation Stephanie Pollack and MBTA General Manager Steve Poftak joined municipal leaders and other elected officials to tour action taking place along the New Bedford Main Line in East Freetown, an area in which culvert work is taking place.

“South Coast Rail Phase 1 will connect Taunton, Fall River, New Bedford, and the surrounding areas to Boston, giving people more options to get to and from southeastern Massachusetts,” Baker said in a statement. “We are proud to advance South Coast Rail further than it’s ever been as part of our administration’s $8 billion MBTA infrastructure investment plan over the next five years.”

The $1 billion project will use a dog-leg route through Middleborough that will open in 2023. The route was chosen over a faster, more direct route through Stoughton due to permitting delays for brand-new sections of track that have to be build in environmentally sensitive areas. The phase 1 project involves rebuilding 29 miles of track and upgrading another 7 miles, while building six new stations. The project has been significantly delayed for many years, although the current project has already attracted development interest.

“Since the first South Coast Rail Groundbreaking Ceremony I attended 21 years ago, the necessity of this project has only become more clear,” state Sen. Michael Rodrigues said in a statement. “The communities of the South Coast deserve to be economically competitive with the rest of the region, and South Coast Rail is a large piece of that.”

The MBTA plans to operate three morning peak trains and three evening peak trains to both New Bedford and Fall River. Taunton and Middleborough will see up to six morning and six evening peak trains because all of the service will pass through those communities. In total, 26 trains each day will run on the line, although during off-peak periods, three trains will operate on a three to three-and-a-half-hour frequency.

South Shore and SouthCoast economic and political leaders believe the commuter rail offers one of the best tools to boost the region’s economy, where demand for commercial space and for homes has significantly lagged the rest of Eastern Massachusetts.