Portal tombs, sometimes called dolmens, are among the most architecturally striking of prehistoric monuments: two tall upright stones at the entrance, or portal, support one end of a large capstone, which tilts dramatically downward toward the rear of the chamber. The overall effect is less like a burial chamber and more like a stone doorway opening onto nothing, which perhaps explains why they have attracted curiosity for centuries.

The Ballyknock tomb was recorded and described by Ruaidhrí de Valera and Seán Ó Nualláin in their 1964 volume covering the megalithic tombs of County Mayo, part of a multi-volume survey that systematically documented prehistoric funerary monuments across Ireland. De Valera and Ó Nualláin's Mayo volume remains a foundational reference for understanding the distribution and structural variety of portal tombs in the west of Ireland, a region that contains a notable concentration of Neolithic monument types. Portal tombs generally date to roughly 4000 to 3500 BCE, constructed by farming communities who had settled Ireland some generations earlier and who used communal burial as one means of marking territory and ancestry.