The problem of a vertical wire antenna placed above a flat lossy ground is formulated analytically in terms of the electric-field type (Pocklington-type) integral equation for current distribution on the antenna. The low-frequency approximation to the Sommerfeld integral appearing in the kernel of the equation is employed in the formulation. A numerical solution is obtained by the use of the piecewise sinusoidal Galerkin method, and the results are compared with those derived from the reflection-coefficient method and with available experimental data. The comparison shows a potential usefulness of the low-frequency approach.