Ed Moses in 2014. (Charley Gallay/Getty Images for Art of Elysium)

Ed Moses, an abstract expressionist who was one of the founding members of a collective known as the "Cool School" and helped transform Los Angeles from a cultural backwater to a major force in the world of modern art, died Jan. 17 at his home in Los Angeles. He was 91.

His son, Andy Moses, also an artist, confirmed the death but did not disclose the cause.

The elder Mr. Moses, who produced hundreds of paintings and drawings and whose work was the subject of countless exhibitions during a career spanning more than 60 years, continued to work almost daily until about two weeks ago, when his health began to fail.

Mr. Moses had his first major exhibition in 1958 at the legendary Ferus Gallery in Hollywood. He became a member of the gallery's post-World War II "Cool School," a group of artists that put Los Angeles on the artistic map with their outsize talents and personalities.

Other members included Ed Ruscha, Billy Al Bengston, Robert Irwin, Edward Kienholz, Larry Bell, John Altoon and Wallace Berman.

Over the next 60 years, Mr. Moses would work tirelessly, transitioning from one style to another.

"The rational mind constantly wants to be in charge," he once said. "The other parts want to fly. My painting is the encounter between the mind's necessity for control and its yearning to fly, to be free from our ever-confining skull."

Early in his career, he gained attention for his "Rose Drawings," the result of tracing rose patterns he found on an oilcloth from Tijuana, Mexico, and repeating them until they created dense abstract fields that spread out seemingly endlessly. One piece in the collection of the Los Angeles Museum of Contemporary Art covers a folding, four-piece panel.

Later he embraced process-based art, working with various materials.

In 2016, the year he turned 90, he debuted a series of craquelure paintings that he created by placing black or white paint on a canvas, adding what he called a "secret sauce," letting it dry and then hitting the canvas with his fist or elbow.

The institutions that hold his works include the Los Angeles County Museum of Art, the Los Angeles Museum of Contemporary Art, the Hammer Museum, New York and San Francisco's museums of modern art and New York's Whitney Museum of American Art.

"Ed Moses has been central to the history of artmaking in Los Angeles for more than half a century," the Los Angeles County museum's director, Michael Govan, said during a major exhibition of his drawings in 2015.

Born in Long Beach, Calif., on April 9, 1926, Edward Moses was conceived in Hawaii by parents who split up before he was born. He said he rarely saw his father, who remained in Hawaii after his mother moved to California.

He briefly pursued a medical career after serving as a surgical technician in the Navy during World War II. After leaving the military, he enrolled in a pre-med program at Long Beach Community College but dropped out after he said he struggled with the curriculum. Before he left campus, however, he took an art class, and the instructor convinced him that art was his true calling.

Enrolling at the University of California at Los Angeles, he would go on to receive a master's degree in fine art. He was a graduate student in 1958 when he had his first Ferus Gallery exhibition.

Later he taught at UCLA and the University of California at Irvine, where one of his students was abstract artist Chris Burden, whose "Urban Light" work stands outside the Los Angeles County Museum of Art.

In addition to his son, Mr. Moses is survived by his wife, the former Avilda Peters; another son, Los Angeles hospitality entrepreneur Cedd Moses; and two grandchildren.

— Associated Press