Surfactant solutions exhibit a wide variety of wetting and dewetting behaviors on high energy surfaces. These behaviors are driven by surfactant self-assemblies at the moving contact line. To probe these self-assemblies, we study the structure Of C12En (1 less than or equal to n less than or equal to 8) surfactants at the three interfaces near a contact line receding across a hydrophilic surface. We determine the area per molecule adsorbed at the solid/liquid (SL) and liquid/vapor (LV) interfaces and the structural details of the monolayer deposited to the solid/vapor (SV) interface at the receding contact line. For all n, the monolayer deposited at the SV interface is substantially less dense than the amount delivered to it by the LV interface, with the SL interface making a small-to-negligible contribution to the deposited monolayer. A dividing streamline must exist in the bulk, along which surfactant from the LV interface is returned to solution. For n greater than or equal to 6 the ethylene oxide headgroups begin to behave like poly(ethylene oxide) (PEO) polymer at the SL interface. At the LV interface the area per molecule increases monotonically with n, suggesting increasing disorder in the headgroup region. The deposited monolayer at the SV interface shows a more complicated, nonmonotonic dependence on n. Processes at the receding contact line and the structure of the deposited monolayer show marked transitions at n = 3, indicating a significant interaction between headgroup and substrate for n > 3.