For the first time in 126 years, the Fernald Developmental Center in Waltham will not be serving people with developmental disabilities.

It’s the end of an era.

For the first time in 126 years, the Fernald Developmental Center in Waltham will not be serving people with developmental disabilities.

The center, popularly referred to as “Fernald,” saw its last resident leave Thursday. At its peak, Fernald was home to more than 2,500 people, which fluctuated, but steadily decreased to just over 300 in 2001.

Former Massachusetts Gov. Mitt Romney, in 2003, thought the state would close Fernald by 2007, but a band of resident advocates fought – and succeeded – to keep it open through ongoing litigation until Thursday, when the last resident moved out to live independently in an undisclosed community.

“It’s a sad day for this part of Waltham’s history, but we look to the future,” Mayor Jeannette McCarthy said Friday.

In 2013, Fernald was home to just 13 residents. This past summer, however, the number dwindled to three before one died, another moved into Marquardt Nursing Center, and the third – and final resident – moved out to a community-run facility.

The city is currently working out a deal with the state to purchase the center and its nearly 200 acres of land off Trapelo Road. In initial discussions, the city was slated to take the land and dozens of defunct buildings, but the state would maintain control over a handful of operational buildings where Fernald residents lived, worked and held recreational activities. The buildings in question included Marquardt (Nursing Center), Malone Park (residential), Greene (pool) and Site 7 (recreation).

The state will continue to operate Marquardt, a skilled nursing facility separate from Fernald, which is run by the Department of Developmental Services and licensed by the federal government. It will also likely continue to run Greene, which is a specialized swimming pool designed for people with developmental disabilities.

McCarthy says the state will also use Site 7 for maintenance, but isn’t sure about Malone Park.

“I think Malone would be in the mix now,” McCarthy said.

A Division of Capital Asset Management and Maintenance (DCAMM) spokeswoman confirmed Friday that the last resident moved out, but wouldn’t comment on how it would affect the deal with the city.

“DCAMM is still working with the City of Waltham on finalizing the sale of the property,” the spokeswoman wrote in an email.

The city is slated to buy land and buildings for about $3.7 million. The mayor currently has a plan to purchase nearly half the land with Community Preservation Act funds and the other half with free cash. Her plan will be considered – and likely voted on – by the Community Preservation Committee on Tuesday.

If approved, it’ll go before City Council for further consideration and a vote.

The Fernald closing marks the end of the oldest publicly funded center for people with developmental disabilities in the Western hemisphere.