A lift assembly for mounting a running board on a vehicle and operational to raise and lower the running board. The lift assembly includes a support structure configured for mounting to the vehicle, a slide assembly slidably supported by the support structure for movement in a longitudinal direction of the lift assembly, arm assemblies pivotably supported by the support structure, and a device for moving the slide assembly relative to the support structure. The slide assembly includes followers that cam with camming members of each arm assembly. Each arm assembly further includes a shaft for supporting the running board. Each shaft is located on its arm assembly so as to move downward and upward when the arm assemblies are pivoted relative to the support structure as a result of the followers of the slide assembly camming against the camming members of the arm assemblies.