WEBSTER GROVES, Mo. (AP) — An Illinois woman has left a $45 million bequest to the Opera Theatre of St. Louis, which will more than double the company’s endowment fund, the company announced Thursday.

The gift from Phyllis Hernden Brissenden, of Springfield, Illinois, will increase the opera’s endowment fund to about $80 million from the current $35 million. The organization said it is one of the largest gifts in American opera history.

Brissenden, 86, was a life board member and generous contributor to the Webster Groves-based company since it opened in 1976. She died of heart failure on Dec. 17 in Springfield, The St. Louis Post-Dispatch reported.

General director Andrew Jorgensen said some income will become available in 2022 but it will be several years, probably not until 2024, before the full effect of the gift is evident because an estate of that size takes time to settle.

Brissenden, whose family owned department stores, was raised in Springfield, Illinois, and worked at United Way in St. Louis during WWII. Her husband, Walter Brissenden, died in 1986. She had no immediate family.

Brissenden was a friend of Opera Theatre founder Elihu Heindman, said founding general director Richard Gaddes.

“She was a faithful sponsor, contributor and supporter from ’76 on,” Gaddes said. “She frequently used to say ‘Opera Theatre is my family.’ Her enthusiasm for Opera Theatre was contagious. She was there a lot. The opera was her life, and she’s acknowledged that in her gift.”

The company said she donated about $2.5 million before her bequest, although she made most of her gifts anonymously.

Brissenden led the company’s National Patrons Council from 2010 to 2017 and made several trips from Springfield to St. Louis every season, seeing each opera as many times as she could.

Opera Theatre of St. Louis will dedicate this season’s production of Carlisle Floyd’s opera “Susanna” to Brissenden.