The adsorption of hydrogen on a cobalt(<10(1)over bar 0>) surface was investigated in ultrahigh vacuum (UHV) between 85 and 500 K using Video-LEED, temperature-programmed thermal desorption (TPD), work function (Delta Phi) measurements, and high-resolution electron energy loss spectroscopy (HREELS). Between 90 and 200 K, hydrogen adsorbs dissociatively with high sticking coefficient (s(0) greater than or equal to 0.8) via precursor kinetics and forms, with increasing exposure, a c (2x4), a p 2 mg (2x1) and a (1x2) LEED structure (hydrogen coverages Theta(H)=0.5, 1.0, and 1.5, respectively). While the first two structures represent true ordered hydrogen phases there is strong evidence that the (1x2) phase is reconstructed, likely in a paired-row configuration. The formation of the (1x2) phase is slightly thermally activated; its decomposition produces a sharp thermal desorption maximum (alpha state) appearing on the low-energy side of a beta-TPD signal which reflects the hydrogen desorbing from the unreconstructed surface. The activation energies for desorption from the alpha and beta states are 62 and 80 kJ/mol, respectively. Chemisorption in the beta state [(2x1) phase up to Theta(H)=1.0] is associated with a Delta Phi of +207 meV, while the fully developed (1x2) reconstructed phase (alpha state) causes a Delta Phi of approximately -122 meV resulting in an overall work function change of +85 meV at saturation. From HREELS, we determine the H adsorption site in all superstructures to be threefold with a local C-s Symmetry. Our results are discussed and compared with previous findings for similar metal-hydrogen interaction systems.