End of Day XXI (1972) belongs to Louise Nevelson’s extensive End of Day series, a group of black-painted wood constructions developed principally across 1972 and 1973. Within the tightly framed relief, slender wooden elements are assembled into an intricate architectural grid, their projecting and recessed surfaces continually altering as light moves across the work. The title situates the sculpture within Nevelson’s longstanding fascination with transitional states - what she described as the “in-between places, the dawns and the dusks” - in which form becomes inseparable from changing patterns of illumination and shadow. The monochrome black surface is crucial to this transformation: suppressing the separate identities of the assembled elements, it draws attention instead to their rhythms, depths and silhouettes. Other works from the End of Day series can be found in major public collections including the Walker Art Center, Minneapolis; the Nelson-Atkins Museum of Art, Kansas City; the Jewish Museum, New York; and the Madison Museum of Contemporary Art.