The initial stages of the growth of cobalt films on the Si(100)2 × 1 surface and the dynamics of variation in their phase composition, electronic structure, and magnetic properties with a coverage increasing in the range 1-20 Å resolution photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in Co 3p electron photoemission. It has been shown that a film of metallic cobalt starts to grow at a coverage of ~7 Å. This process is preceded by the stages involving the formation of the interface cobalt silicide and the Co-Si solid solution. It has also been demonstrated that, at coverages below 15 Å, the sample surface is coated by segregated silicon. The ferromagnetic ordering of the film in the surface plane has been found to follow a threshold character and set in at a coverage of ~6 Å. A further increase in the coverage in the range 8-16 Å is accompanied by a slower increase in the remanence of the film.