ORANGE, Calif. — Arvella Schuller, who helped her pastor husband found the Crystal Cathedral megachurch in Southern California and hallmark “Hour of Power” televangelism program seen by millions of viewers around the globe, died on Tuesday. She was 84.

Schuller, who was married to the Rev. Robert H. Schuller, passed away unexpectedly at University of California, Irvine Medical Center in Orange after a brief illness, said her daughter, Carol Schuller Milner.

Schuller helped her husband start a ministry at an Orange County drive-in movie theater in 1955 and grow it into a megachurch — housed in a landmark glass-paned building — with a global television reach.

Arvella Schuller was born and raised in a farming community in Iowa. She was the organist at her husband’s church at the drive-in and served as executive producer and program director for the “Hour of Power” worldwide television ministry, which began broadcasting in 1970. She also developed a private school affiliated with the church, according to ministry officials.

At its peak, the “Hour of Power” broadcast attracted 20 million viewers, but it saw a decline in viewers and donations after a rocky leadership transition.

The ministry filed for bankruptcy in 2010.