From 1964 to 1965, Robert Morris made a series of lead relief sculptures, which have been almost completely excluded from the literature on his work, even though they comprise one of the largest groups in his oeuvre. This essay argues that the leads express key epochal anxieties from 1960s America regarding materiality, labour and 'social abstraction'. It tracks a consistent ambivalence within the leads, which oscillate between presenting invisible forces or troubling abstractions, and resisting them through literal materiality or nostalgic associations. The leads - and related works including Morris's performance War (1963) - are linked with socio-political issues including the 'military industrial complex' and the rise of automation. Morris's reliefs are also contextualized in relation to his better known minimal sculptures, broad trends amongst his contemporaries, and the work of Marcel Duchamp and Jasper Johns.