Secular, annual, and semiannual changes were obtained from the midnight values of field on specially determined days of quiet magnetospheric conditions. From a selection of North American observatories the latitude variation of these changes was evaluated from 20° to 65°. Results for the active and quiet sun years (1958 and 1965) were compared, and changes at Tucson were traced from 1958 through 1974. The year‐to‐year variance in the determination of a secular change seemed to be decreased by the present analysis method in comparison to a method which uses the annual mean of hourly values. The annual horizontal field variations were largely northward in early summer and southward in early winter; quiet year amplitudes of 2 to 3 γ about doubled in the solar active year. The amplitudes of the semiannual field vectors were about one half that of the annual vectors; the directions were apparently inconsistent from year to year.