Times certainly have changed... To add to LeadSled's comment, here is the actual US rule change issued December 1, 1959 and effective March 15, 1960:
Civil Air Regulations Amendment 41-29 - Maximum Age Limitations For Pilots
More recently, here are links to the studies conducted by the FAA Civil Aerospace Medical Institute related to the "Age 60 Rule":
94/20 Age 60 Rule Research, Part I: Bibliographic Database - A
94/20 Age 60 Rule Research, Part I: Bibliographic Database - B
94/20 Age 60 Rule Research, Part I: Bibliographic Database - C
94/21 Age 60 Rule Research, Part II: Airline Pilot Age and Performance A Review of the Scientific Literature
94/22 Age 60 Rule Research, Part III: Consolidated Database Experiments Final Report
94/23 Age 60 Rule Research, Part IV: Experimental Evaluation of Pilot Performance
04/8 Methodological Issues in the Study of Airplane Accident Rates by Pilot Age: Effects of Accident and Pilot Inclusion Criteria and Analytic Strategy