The variation of interplanetary parameters at Earth orbit has previously been studied by superposed-epoch analysis of the spacecraft dataa obtained during solar cycle 20. It was shown that the magnetosonic speed possesses a quasi-steady, but slightly drifting, distribution in Carrington longitude during all phases of solar cycle 20. Other magnetic parameters such as the Alfvenic speed and ratios of magnetic and total pressure to the kinetic energy density also reflect this same organization in Carrington longitude in both the maximum and minimum years. We extend the study of the quasi-steady corotating solar-terrestrial variation to include the long-time series of geomagnetic index C9 data covering solar cycles 13--20. Using the superposed-epoch method in conjunction with digital filter and harmonic analysis, we find that during solar minima the corotating variation has a quite steady structure of distribution in the Carrington rotation, with the phase of the second harmonic remaining nearly the same in each of the even or odd cycles, and it is likely that their source regions are located in the northern and southern solar hemispheres, respectively, for the first and second peaks within each rotation. In addition, the locations of the peaks in the even cycle minima show only a small systematic drift in heliospheric longitude (about 6 Carrington days, net) from 1913 to 1974. The implication is that the stable high-speed solar wind streams originate from a deeply rooted configuration of the general solar magnetic field which persists for at least four solar cycles.