Variations in solar wind ion characteristics observed between March 18, 1971, and January 6, 1977, are presented in order to study long-term trends in large-scale interplanetary structures. Salient features observed during this period include the following. (1) Large amplitude, broad, corotating high-speed streams appeared in January 1973 and disappeared in mid-1976 and resulted in enhanced average flow speeds during this epoch of solar activity cycle 20. (2) Both proton number and total energy fluxes were generally larger after September 1972 than before August 1972. This increase is thought to result from an areal expansion of both polar coronal holes in response to the increasing polar field magnitudes and to lead to a compression of the low-speed equatorial disclike region postulated to surround the sun in interplanetary space. (3) The occurrence frequency of density enhancements not obviously produced by interplanetary compressions did not decrease with decreasing solar activity. It therefore seems unlikely that all such enhancements are caused by coronal transient events. (4) The average solar wind He abundance varied from about 3 to 5% and back to 3% during activity cycle 20. This variation lagged behind that of the smoothed sunspot number by about 1--2 years. The abundance variations, like all other known systematic solar wind ion variations, occurred preferentially during low-speed and/or high-density flow conditions. This result may be caused by a systematic time variation in the mixture of coronal flow types leading to low-speed conditions at 1 AU. Near solar maximum, energetic transient disturbances may dominate, while near solar minimum, spatially structured high-density expansions may dominate.