The changing size and composition of the older population from 1900 to 2000 are examined from a cohort historical perspective. Successive cohorts occupying the age category 60-64 at the beginning of each decade are compared with respect to size, nativity status, rural-urban status, and educational status. It is found that the demographic processes producing change in these variables are transitional phenomena, and that the period of most rapid change is now over. For the remainder of this century, changes in size and demographic characteristics of cohorts entering old age will occur at a slower pace than in the recent past.