Midpassages are the most recognizable architectural feature associated with the entire Paleoeskimo period (2800 BC–AD 1300) in the Canadian and Greenlandic Arctic. Usually built of stone, midpassages are rectangular-shaped axial structures that run through the center of tent rings and semisubterranean house depressions. However, a unique triangular form of midpassage developed in association with the Late Dorset complex in the Boothia Peninsula area of the Canadian Arctic around AD 400. Unlike the rectangular-shaped varieties that were built contemporaneously across the Arctic, distribution of the triangular form is limited, and occurrences are rare. Initially, construction appears restricted to the Boothia Peninsula region, where the form persisted for the subsequent 400 years. After AD 900, they are found in Inglefield Land, Greenland, and a few other locations in the Canadian Arctic where they continued to be built until around AD 1200, representing an over 800-year period in a remarkably unvarying configuration. Further, these triangular midpassage structures very likely represent a regional architectural variant that moved northward with the Late Dorset diaspora after AD 800.