[6] While this became his signature style in the eyes of some critics and curators, Gilliam mostly moved on from his Drape paintings after the early 1980s, primarily returning to the form for several commissions and a series of late-career pieces, usually created with new techniques or methods that he was exploring in his other work.

[12] Late-career milestones included creating a work for permanent display in the lobby of the then-newly opened National Museum of African American History and Culture in 2016, and exhibiting for a second time at the Venice Biennale in 2017.

[13] Gilliam said that his father worked variously as "a farmer, a baseball pitcher, a deacon, a janitor," in addition to being a hobbyist carpenter;[14] his mother was a school teacher, cared for the large family,[7] and was an active member of the neighborhood sewing group.

[24] While in Japan he visited Frank Lloyd Wright's Imperial Hotel prior to its demolition in 1967,[24] learned about the Gutai Art Association, and was introduced to the work of Yves Klein at an exhibition in Tokyo.

"[28] He was inspired in large part during this period by several artists associated with the Bay Area Figurative Movement, including Richard Diebenkorn, David Park, and, in particular, Nathan Oliveira, whose work he had been introduced to by Wilke, his undergraduate professor, and by seeing the exhibition 2nd Pacific Coast Biennial, which traveled in 1958 to Louisville's Speed Art Museum.

[21] Butler earned her master's degree from Columbia while Gilliam remained in Louisville, and he traveled to New York to visit her often,[32] where he also became interested in work by Hans Hofmann, Barnett Newman, and Mark Rothko.

[33][23] Gilliam began to work wholeheartedly in abstraction, continuing to travel to New York and researching notable contemporary artists, experimenting in depth with their theories, styles, and methods in order,[33] in his words, "to get away from the look of so many painters who were capable of opening my eyes.

[41] Although Gilliam had been deeply engaged as an activist in college, critic Vivien Raynor would later write that he had "emerged disenchanted," feeling that "the sum total of his activism had amounted to little more than gaining political honors for others.

[42] Reflecting on this period two decades later, critic John Russell wrote that Gilliam "stood firm for his own kind of painting at a time when abstract art was said by some to be irrelevant to black American life.

"[54] Downing also introduced Gilliam to methods and materials used by the cohort, such as how to work with Magna acrylic resin paint which can soak into canvas rather than layering on top of it, along with a water-tension breaker, the group's so-called "secret ingredient.

[56] Paintings by Gilliam from this period of hard-edge abstraction include Shoot Six, which showcased how he was moving beyond the Washington School's core styles, as the distinct regions of colors blend together in the lower-right corner.

[67] Gilliam was able to leave his teaching position at McKinley to focus on his painting in the run-up to the exhibition, thanks to an individual artist's grant from the National Endowment for the Arts (NEA),[68] which he also used to purchase a home in the Mount Pleasant neighborhood.

[104] Baroque Cascade in particular was broadly acclaimed by critics as marking a singular achievement in combining painting and architecture to explore space, color, and shape,[105] with LeGrace G. Benson writing in Artforum that "every visible and tactile and kinetic element was drawn into an ensemble of compelling force;"[106] Forgey later called the exhibition "one of those watermarks by which the Washington art community measures its evolution.

[137] These works, begun by staining canvases with color and stretching them over beveled wood similar to his Slice paintings,[138] were then covered in layers of white acrylic glaze and flocking applied with lacquer thinner, before being placed in custom aluminum frames made in collaboration with Stovall.

[148] Around this time Gilliam began experimenting with assemblage, culminating with Dark as I Am, a mixed-media work that existed in the artist's studio in various forms for five years before he exhibited it as an immersive installation at Jefferson Place Gallery in November 1973.

[162] Seahorses was made with traditional canvas material displayed open to the elements and was blown off the museums' walls by the wind in both Philadelphia and Brooklyn,[171][15] and the canvases were tattered and partly destroyed by the time he deinstalled them in New York.

[179][180] He continued experimenting with new surface qualities and textures, using different paints, hardeners, and physical materials in a specific combination he later said he could no longer remember, producing layered black compositions on top of the collage that resembled rocky tar or asphalt and extended over the beveled edges of the rectangular canvases.

[181][180] Works like Azure and Rail exemplify this series,[173] with flecks of bright color and outlines of sharp geometric shapes partly visible under a thick impasto of black paint.

[173] Gilliam's new critical successes led to rising prices for his work, allowing him to purchase a building near 14th and U St NW in 1979[note 4] that he shared with Krebs and which served as his primary studio for over 30 years,[182] in exchange for $60,000 and three of his paintings.

[183] He also experimented with stretching the stained and collaged canvases over irregular polygonal beveled stretchers each with nine distinct edges, before covering them with raked fields of paint,[184] producing seventeen of these new forms that he called Chasers.

"[7] Binstock argued that Gilliam's choices to pursue abstraction as a black artist and to not have a permanent gallery contributed to what he deemed "a process of growth or expansion and then perhaps a cooling or retrenching period.

"[8] Speaking in 2013, Gilliam offered another explanation as to why he may have been overlooked by some in the art world, suggesting that younger post-black artists making work during this era had been "able to do something I was not – to keep the political in the front," and that they had received greater attention for it.

[194][195] Additionally, several authors - and Gilliam's family[48] - rebutted the idea that his career truly declined, given the breadth of exhibitions he staged and participated in during the period, and suggested in retrospect that this was an overdramatized narrative.

"[199] Throughout the 1990s Gilliam completed a number of public and private commissions in relatively quick succession, received several grants, and regularly sold his work,[48] with consistent acquisitions at museums and galleries at HBCUs in particular.

[11] Beginning in the early 2000s, Gilliam returned to a new version of his early-career geometric abstractions;[208] after experimenting with making monochromatic print works in 2001 at Ohio University, he developed a series of monochrome paintings on wood that he first called Slats and later renamed Slatts.

"[48] Gilliam staged an exhibition of his early hard-edge abstract paintings in 2013 at David Kordansky Gallery in Los Angeles, curated by the younger artist Rashid Johnson, which brought a new wave of national media attention to his work.

[48] Throughout the next decade Gilliam participated in a large number of high-profile solo and group shows and created several new commissions,[7] including a permanent installation in the lobby of the newly opened National Museum of African American History and Culture in Washington, in 2016.

[226] In 2020 he staged his first solo show with Pace,[227] premiering a new body of stained and painted monochrome wooden sculptures, some in the form of small pyramids on casters that can be displayed in different combinations, which had been inspired by his time in Basel, where he said he saw many recently arrived migrants, leading him to think more deeply about the shapes of what he called "early Africa.

His first work made for permanent public display was Triple Variants, an unstretched canvas in earthy tones with extensive cut-outs, bolted flat and draped against the wall, with two curved blocks of marble and an aluminum beam resting on the ground.

In the artist's words, the predominant blue offers "a visual solid in a transitional area that is near subterranean," and the work calls to mind "movement, circuits, speed, technology, and passenger ships".