The Science Museum of Minnesota announced Wednesday that it received a $1 million gift to pay for operations — the largest donation of its kind in the nonprofit's recent history.

In an unusual step, the donor — who wishes to remain anonymous — told the St. Paul museum the money could be used for its general operations, not designating it for a specific program or initiative. That kind of donation, called an "unrestricted gift," is becoming increasingly rare in philanthropy, especially among corporate and foundation donations, said Mimi Daly Larson, the museum's vice president of mission advancement.

"We're grateful these are flexible dollars that support our mission," she said. "It's getting harder to raise unrestricted dollars that are so critical to running the organization and delivering our mission."

From the Greater Twin Cities United Way to the Target Foundation, more funders are narrowing the focus of their grantmaking. Others are decreasing their giving or shifting away from "unrestricted gifts" because they want donations to align more with their organization's mission, Larson said.

Individual donors are still giving a mix of donations that are restricted or unrestricted, she said, but the nonprofit relies more on corporations and foundations for revenue.

The museum, which has an annual budget of about $40 million, drew about a third of that in revenue from donations, grants and government contracts in 2017. Nearly $18 million came from admission fees and other program fees, according to tax forms.

Now, Larson said the latest $1 million from the donor, who has supported the Science Museum in the past, helps "put us ahead of where we thought we'd be" this time of year in terms of fundraising before the nonprofit's fiscal year ends in June. Other years, the museum has had to tap into its endowment to cover expenses.

Founded in 1907 as a natural-history museum, the Science Museum is best known for its lab experiments and dinosaur exhibits. But it's also broadened its focus in recent years — from adding an exhibit on race and mental health to creating its own exhibits and reinvesting in its own scientific research done by nearly two dozen in-house scientists.

The museum along St. Paul's Mississippi River attracted more than 800,000 visitors in 2017 and also provides education programs for students in every county of the state.

Kelly Smith • 612-673-4141