Integrin αβ heterodimers mediate cell−cell and cell−matrix interactions and provide the traction for most cell migration in the body1,2. Integrin ectodomains are unusually large and complex and assume three global conformational states (Fig. 1a) that differ up to 1,000-fold in affinity for ligand2. Antigen recognition by lymphocytes as well as firm adhesion, diapedesis, and migration of leukocytes within tissues are dependent on lymphocyte function-associated antigen-1 (LFA-1), i.e. integrin αLβ2 or CD11a/CD18. Binding of LFA-1 to intercellular adhesion molecules (ICAMs) by the integrin head is communicated by 10 leg domains, through single-span transmembrane domains in each subunit, to the cytoskeleton via adaptors such as talins and kindlins3. How do integrins couple extracellular ligands to the actin cytoskeleton through a molecular mechanism that enables cell migration? Here, we test molecular predictions of a cytoskeletal force model of integrin activation4 in live cells. Using green fluorescent protein (GFP) inserted by fusing its N and C-termini to the LFA-1 head and polarization microscopy, we show that LFA-1 molecules engaged to ICAM-1 and the cytoskeleton are aligned and oriented relative to the direction of retrograde actin flow5,6 at the leading edge of migrating lymphocytes. Realistic 3D models of GFP-head fusions relate the transition dipole orientation of the GFP fluorophore7,8 to the orientation of engaged LFA-1 molecules on the cell surface. The orientation of the transition dipole in two distinct fusions correlates to the orientation of retrograde actin flow at the leading edge of migrating cells as measured by live-cell structured illumination microscopy. Alignment is dependent on cytoskeleton coupling to the β2 cytoplasmic tail and is consistent with integrins with a specific tilt being oriented in the same direction as retrograde actin flow. Together, these results strongly support the cytoskeletal force model of integrin activation and place the atomic structures of integrins in the context of cellular length-scale measurements that define how integrins orient as they function in leukocyte migration.