SAN FRANCISCO - The San Francisco Museum of Modern Art will exhibit a large collection of important 20th century art amassed by the founders of the Gap apparel chain including pieces by Warhol, Lichtenstein and de Kooning.

The museum, also called SFMOMA, will interweave 1,100 works of art collected over 40 years by Gap Inc founders Donald and Doris Fisher with its existing collection, the museum and the Fisher family announced.

The works are due to be housed permanently at the museum and are set to be exhibited to the public for the first time next year. Some of the works have been shown previously on a rotating basis at Gap's San Francisco headquarters.

The agreement with the Fisher family represents a coup for the museum, elevating its profile among institutions around the world that house modern art. The Fisher family will create a trust to be administered in collaboration with the museum to oversee the care of the collection.

The museum did not offer an estimate of the value of the collection, which includes paintings and sculptures by Andy Warhol, Roy Lichtenstein, Willem de Kooning and other important 20th century artists.

A major expansion of the museum, which is already underway, will include a special gallery for the new works. An exhibit of the collection is planned for next summer.

The family's agreement with the museum came after the Fishers' original plan to build a museum in the city's Presidio -- a former Army base that is now a national park -- fell through amid local opposition.

SFMOMA, which was founded in 1935, was the first U.S. West Coast museum devoted to modern and contemporary art. Its collection currently includes more than 26,000 works housed in a five-story structure with a central atrium built in 1995 and designed by Swiss architect Mario Botta.

The new collection will "provide visitors with a deeper, fuller view of key contemporary artists and movements," SFMOMA Director Neal Benezra said in a statement.

"The Fisher collection is a perfect complement to the museum's strong holdings of artists like Gerhard Richter, Andy Warhol and Philip Guston, and gives us new strength in our representation of major figures like Alexander Calder, Anselm Kiefer, Richard Serra and Chuck Close," Benezra said.

"San Francisco is where we raised our family and opened our first Gap store, and we want to give back to the city we love by sharing the art that means so much to us," Donald Fisher said in a statement.