An analytic representation of the quiet daily variation of the geomagnetic field (Sq) was obtained for 1965 in the North American region, with a mean error of less than 10% of the daily variation range. The month-by-month 24-, 12-, 8-, and 6-hour Fourier components of the field in H, D, and Z had significant annual and semiannual changes. At the equator the Sq(Q) semiannual changes was dominant for all Fourier components. From 15¿ to 50¿ latitude the 24-hour component annual change of Sq(D) was the principal seasonal variation in this region of the ionospheric current vortex. Great enhancements of the 24-hour component of the daily field occurred at high latitude, with strong summertime maxima in the annual variation of H, D, and Z above 70¿ latitude. The results, in general, agree with the expectation for ionospheric current sources in all regions.