Pulsed molecular beam-surface infrared measurements of the kinetics of CO populating step sites on Ni(9,1,1) are reported and interpreted in terms of elementary surface rate processes. An analytic model is developed to describe the distribution of CO between step and terrace sites in the equilibrium limit, and refine our previous determination of the binding energy difference between these sites to Delta E(s-t)=0.6+/-0.2 kcal/mol. Time-resolved surface infrared measurements indicate that the equilibrium step coverage is reached within 100 ms of the chemisorption event. This rapid migration across the (100) terraces to step sites implies a barrier to surface hopping of <5.5 kcal/mol. On a longer time scale of minutes, the CO population at step sites increases further as the equilibrium point is shifted by the dissociative adsorption of residual hydrogen. These slower step filling rates are described with a kinetic model, in which hydrogen adsorption is the rate-limiting step.