The Croswell Opera House has received a $2.5 million gift from Adrian native Julianne Argyros and her husband, George.

The gift is the single largest donation in the Croswell’s history. Argyros made her surprise announcement at The Great Big Night, the Croswell’s annual fundraising gala, just before the curtain rose on opening night for the musical “Billy Elliot.”

The Croswell announced a capital campaign to renovate the historic theater in June 2015.

Argyros, whose ties to the theater go back to her childhood, told the audience that the community response to the Croswell’s campaign has been unlike anything her family’s foundation has seen.

“We give a lot of grants at our foundation,” she said, “and I can tell you we have never, ever, ever seen the heart and the spirit and the love that went into this campaign that you organized. It was phenomenal.”

Croswell artistic director Jere Righter said the Argyros’ donation is “an amazing gift for our future.”

“We are so grateful for George and Julia’s generosity and for the faith they have shown in the Croswell and its role in our community,” she said.

Croswell board president Emory Schmidt said the public response to the campaign has been “overwhelming.” In addition to the success of a crowdfunding effort last year, the campaign has gained support not just from individual, corporate and foundation donors — including the Sage Foundation and the Steve and Sally Hickman family — but also from community groups like the Adrian Kiwanis and Rotary clubs.

“The broad base of public support for this campaign is really what helped us demonstrate its viability,” Schmidt said. “None of this could have happened without the incredible support we have received from our community.”

The capital campaign had an initial goal of $6.2 million, and the Croswell board later set a “stretch goal” of $7.2 million.

Up until Saturday, the Croswell had raised just short of $5.2 million, so the Argyros’ gift will put the theater over both targets. However, to guard against unexpected complications with renovating the 150-year-old building and to build an endowment large enough to make an impact on long-term financial stability, some fundraising will continue through the end of the year.

The Croswell’s renovations, which are scheduled to be finished in spring 2017, are aimed at updating the theater’s infrastructure and providing new programming opportunities while staying true to its historic character.

Julianne Argyros grew up in Adrian and graduated from Adrian High School in 1958. She met her husband while attending California State University at Long Beach. George Argyros, a graduate of Chapman University, became successful in real estate and owned the Seattle Mariners from 1981 to 1989. He served as the U.S. ambassador to Spain from 2001 to 2004.

Through the Argyros Family Foundation, they have supported numerous arts, educational and health care organizations, both in California and across the United States. Their gift of $1 million to the Croswell in 2013 helped launch the capital campaign. They are also supporters of the Adrian Schools Educational Foundation.

The Croswell, which opened in 1866, is the oldest theater in Michigan and one of the oldest continuously operating theaters in the United States.