Calling it an “extraordinary” gift and the largest in the school’s history, the president of Gustavus Adolphus College in St. Peter, Minn., said the institution received a $25 million donation from a Twin Cities family.

The money will help pay for a planned $65 million redo of the school’s 52-year-old Alfred Nobel Hall of Science.

“It is wonderful news for us,” said Gustavus President Rebecca Bergman.

The school hopes to break ground on the renovation and expansion project in a year to 18 months, she said. Bergman said it’s unclear for now if Gustavus will pay for the new science hall without taking on additional debt.

The donors behind the $25 million gift wished to remain anonymous, but their family includes five Gustavus graduates, said Tim Kennedy, a spokesman for Gustavus.

Their gift is among the largest ever to a Minnesota school, and one of the largest in the past few years. University of St. Thomas landed a $60 million gift in 2007 and a $50 million gift the following year.

The donation comes as the school wraps up a $150 million fundraising campaign begun four years ago. The Carl and Aune Lind Family Foundation gave $3 million to Gustavus earlier this year.

Gustavus chemistry professor Scott Bur said the school’s science hall was built amid the Sputnik-era push for science and technology. Decades on, the building needs renovations to fit modern equipment and up-to-date teaching methods.

“Some of the instrumentation that we have today, that’s essential for us to do our job, didn’t exist when we built this building,” he said.

The new science hall will be the latest in a string of renovations and new construction projects at Gustavus in recent years. The $30 million Warren and Donna Beck Academic Hall opened in 2011. A football stadium, a soccer and track complex and a new residence hall were all built in the past 15 years.

The renovations help draw students as schools nationwide face a shrinking pool of students. The number of Americans turning 18 each year started to drop in 2009, and is expected to continue through next year.

“I want our campus to be a place that attracts students, and so at a certain point if you allow your facilities to be old and tired you’re going to have trouble,” said Bergman.

The school’s enrollment has held steady at about 650 students in the incoming class and 2,400 to 2,450 overall. A quarter of the students are expected to graduate with science degrees, according to the school.

The largest gift to Gustavus before this week was a $16 million donation in 2011 from a Twin Cities couple, Gustavus graduates. They also asked to remain anonymous.

Gustavus is a private, four-year, liberal arts college founded in 1862 and affiliated with the Evangelical Lutheran Church in America.