Dorothy Vogel a librarian who, with her postal-clerk husband, Herbert, bought thousands of works from future art stars, stashing them in their cramped one-bedroom New Yor apartment and eventually handling over the entire collection to the National Gallery of Art, died on Nov. 10 in Manhattan. She was 90.

Throughout their decades as collectors, Ms. Vogel worked at the Brooklyn Public Library as a reference librarian, and Mr. Vogel, a high school dropout from Harlem, did the night shift at a post office sorting mail. Their formal training in art consisted of the art classes Mr. Vogel took at New York University as a young man and a few painting lessons the couple took together.

Their rent-controlled apartment on Manhattan’s Upper East Side functioned as a fine-art storage locker and an exhibition space. Stacked on the floor and crammed into closets were some 4,000 works by Roy Lichtenstein and other luminaries. Nevertheless, the Vogels lived frugally, did not own a car and often ate TV dinners. They bought what they could afford from underground artists.

By the early 1970s, the Vogels had become a known quantity on New York’s avant-garde scene. In 1971, the couple agreed to spend three months cat-sitting for Christo who, with his wife and collaborator Jeanne-Claude, was becoming famous for his monumental works of environmental art. Early on, Christo and Jeanne-Claude had assumed the Vogels were wealthy collectors. “Christo,” Jeanne-Claude said, “it’s the Vogels. We’re going to pay the rent.”

“They didn’t know” Mrs. Vogel said, “that we could barely pay the rent ourselves.”