Jennifer Bartlett, a New York artist whose Conceptual paintings executed on one-foot-square white enameled steel plates (inspired by the city’s subways) blossomed into “Rhapsody,” a landmark extravaganza of painting more than 153 feet long, died on July 25 at her home in Amagansett, N.Y. She was 81.

Her death was jointly announced by her New York representatives, the Paula Cooper Gallery and the Marianne Boesky Gallery.

Her daughter, Alice Carrière, said that while Ms. Bartlett had struggled with dementia, the cause of death was acute myeloid leukemia, diagnosed in early July.

Ms. Bartlett was an unrepentant maverick who started out as a fringe member of the post-Minimalist generation, Conceptual Art Division, devising mathematical or geometric systems that she need only execute, without further aesthetic decisions. She characterized this as a “What if?” approach.

With “Rhapsody,” an important turning point in late-20th-century American art, Ms. Bartlett integrated Conceptualism’s cerebral style with her medium of choice, painting — often to the chagrin of artists on both sides of the painting/non-painting aisle. She also breached the wall separating abstraction and representation, as did painters like Neil Jenney, Lois Lane, Susan Rothenberg and Joe Zucker. But with “Rhapsody,” the break was epic, noisy and permissive.

The work was first exhibited in 1976 at the Paula Cooper Gallery in SoHo, where its 987 plates occupied all the available wall space. Later, to the surprise of many, it seemed tailor-made for the enormous atrium of the Museum of Modern Art, whose collection it entered in 2005, a gift from the architect and collector Edward R. Broida.

Reviewing “Rhapsody” in The New York Times, the English critic John Russell called it “the most ambitious single work of new art that has come my way since I started to live in New York.” It summed up aspects of Pop, Minimalism, and Conceptual and process art, while also opening art anew to images, narrative, repeating patterns, appropriation and stark juxtapositions that continue to inform painting.

Its images span numerous styles, from photorealist to naïve, with several modernist ones in between. It explores line, shape and color as ends in themselves, while also laying out the simple themes that would preoccupy Ms. Bartlett for the rest of her life: tree, mountain, house and ocean.

Each steel plate in “Rhapsody” was printed with a grid of quarter-inch squares, to which she added dots according to whatever system she had set up, sometimes with results that seemed computer-generated.

She characterized the work as a “conversation” — “in the sense that you start explaining one thing and then drift off into another subject to explain by analogy and then come back again.” But it is a tumultuous one, full of interruptions and arguments and, it seems, with everyone talking at once.

“Rhapsody” made Ms. Bartlett a star, though it was not universally loved. Indeed she had doubts of her own, especially since she did not see it complete until it was installed at Paula Cooper. She worried, she told the writer Calvin Tomkins for a 1985 profile in The New Yorker, that the work might be the worst idea she had ever had. The title “Rhapsody,” suggested by a friend, “was so awful I liked it,” she said.

“The word implied something bombastic and overambitious, which seemed accurate enough,” Mr. Tomkins quoted her as saying.

She liked to recount, as she did in a 2011 oral history interview for the Archives of American Art, how one prominent New York curator had said of her dotted surfaces, “That’s not painting, that’s knitting.” (The words echoed Truman Capote’s dismissal of Jack Kerouac’s “spontaneous” prose — “That’s not writing, that’s typing.”)

In the New York of the 1970s and ’80s, Ms. Bartlett was one of the first artists of her generation to live off her work, which she did sometimes lavishly and sometimes not — budget was not part of her vocabulary — while often helping friends and family members in need. She was also one of the first to work directly with out-of-town dealers rather than through her New York representatives.

When New York’s attention faded in the 1990s, she developed an extensive network of galleries in other cities, where she mounted scores of shows of new work. At Locks Gallery in Philadelphia alone, she had over 20 solo shows from 1994 to 2021, usually accompanied by catalogs.

Ms. Bartlett took a 20-year hiatus from showing at Paula Cooper beginning in 1996; during that period she rarely showed in New York and, when she did, usually hopped from gallery to gallery. Her work seemed more popular — and salable — outside the New York art world. In 2016, Ms. Bartlett resumed showing with Ms. Cooper, who joined forces with Ms. Boesky in 2018.

Ms. Bartlett was a stylishly dressed, opinionated, prodigiously prolific artist. Despite seeming to spend a lot of time lying on a couch with a cigarette in one hand and a drink in the other, she said she would go crazy if she couldn’t work. And work she did: painting, printmaking and drawing, especially in pastels, and designing furniture, glassware and jewelry, with limited forays into set and costume design.

With all that, she found time to read voraciously; give lengthy, entertaining interviews; write an autobiographical novel, “A History of the Universe”; and play a big part in the redesign and furnishing of three substantial live-work residences in New York City: two in Lower Manhattan — a big loft on Lafayette Street and a cast concrete industrial building on Charles Street (to which she added an intricate garden designed with Madison Cox and a top-floor lap pool) — and one in Brooklyn, a former union hall in Fort Greene, whose ambitious specimen-tree garden featured large rocks trucked in on a flatbed.

During her marriage to the German actor Mathieu Carrière, from 1983 to 1993, she lived half the year in a large Paris apartment — furnished almost entirely in modernist designs by the Finnish architect Alvar Aalto — in a building where “Last Tango in Paris” was filmed, as she rarely failed to tell anyone who visited.

Ms. Bartlett was as systematic in her life as in her art. Arriving in New York in the late 1960s, she sidestepped bohemianism, instead wearing pearls, sweater sets and poodle skirts in tartan wool, whose plaids would frequently figure in paintings as real-life grids. For a long period, starting in the late 1970s, she wore only the minimalist fashions of Zoran and, later, those of Ronaldus Shamask. Almost without variation she wore her hair short or bobbed with bangs.

She loved lists; her novel incorporated several. At the beginning of her career, she made lists of art ideas and then marked the ones that she thought other artists “owned.” And, in her slightly brassy, ironic monotone, she often talked lists.

At the start of a 1985 interview, Ms. Bartlett’s friend and fellow painter Elizabeth Murray, asked her what had been on her mind when they met in 1962 as students at Mills College in Oakland, Calif. She replied, “Being an artist, Ed Bartlett, Bach cello suites, Cézanne, getting into graduate school, getting to New York, Albert Camus, James Joyce.”

She was born Jennifer Ann Losch in Long Beach, Calif., on March 14, 1941, to Edward and Joanne (Chaffee) Losch. Her father was an entrepreneur whose main business was a pipeline construction company; her mother had attended the Otis Art Institute in Los Angeles and worked as a fashion illustrator until she had children.

Jennifer, the eldest of four, was precocious. She drew constantly, beginning in childhood; loved the ocean and swam in it regularly (she also drew large renderings of sea creatures); found inspiration in her mother’s single art book, on French Post-Impressionism; and was thrilled by a Van Gogh exhibition she saw in Los Angeles. She emerged from high school determined to be a painter.

After graduating from Mills in 1964, Ms. Bartlett married Edward Bartlett, a Stanford graduate, and the two went to Yale for graduate school, he in medicine and she in art. (They divorced in 1972.) In the Yale art department, current students, recent graduates and their friends included some of the most ambitious and competitive artists of her generation: Brice Marden, Richard Serra, Joel Shapiro, Chuck Close, Lynda Benglis and Nancy Graves. After moving to Greene Street in SoHo in the late 1960s, she became friends with the artists Joe Zucker, Jonathan Borofsky, John Torreano, Joe Brainard and Alan Saret, who staged her first solo show in New York in his Spring Street loft.

When she arrived in New York, Ms. Bartlett, inspired by the art of the leading Conceptualist Sol LeWitt, was developing systems on graph paper, which she usually damaged or wore out. One day it occurred to her that New York City subway signs “withstood a lot of punishment,” she said in her Archives interview. They suggested, she said, “a hard grid paper that was impervious to me.”

The 12-inch-square plates based on the signs had the added convenience of being small units that were easy to work on, pack and transport, but that could also assume monumental scale when installed. She liked the enameled steel’s enduring “freshness,” she said; it would not age physically or look dated. Once she worked out the production of the steel plates with a small fabricator in New Jersey, she destroyed her previous paintings.

Her gridded plates represented Ms. Bartlett’s consuming interest in the mechanics of painting, and she would use them for the rest of her life, as in two more epic plate pieces, “Recitative” (2007) and “Song” (2009-10).

She also expanded her materials. Her next big project after “Rhapsody” was “In the Garden,” a suite of nearly 200 drawings of a decrepit garden behind a small villa in Nice, France, where she spent the winter of 1979-80. These works became the basis for large paintings — on plates, oil on canvas and enamel on glass — and several different kinds of prints.

“In the Garden” was also important because Ms. Bartlett worked from life, in particular her immediate surroundings, including, eventually, her studios, her homes and her own gardens. The 1991-92 “Air: 24 Hours” consists of 24 large canvases, each depicting one of these locations at a particular hour of the day. She depicted her living spaces once again in 1992-93 with “24 Hours: Elegy,” usually including a garment or a toy belonging to her daughter. In these works, dense buildups of hand-painted grids create a granular atmosphere reminiscent of those created by Georges Seurat’s dots.

In 2012, a hospitalization of several weeks — caused by what her daughter, Ms. Carrière, described as “a series of symptoms that never quite coalesced into a diagnosis” — resulted in the “Hospital Paintings,” an uncharacteristically stark, realistic group of 10 canvases. Each was disrupted by a thick, arbitrary line of color running edge to edge.

In addition to her daughter, Ms. Bartlett is survived by her sister, Julie Losch Matsumoto.

Ms. Bartlett, insuperably confident and independent, was often asked about her view of feminism, as she was in 2011 for the Archives of American Art. In that instance she answered: “I’m not naturally the feminist type. I just wanted to be the best artist.”