Lyndon Johnson actually said...
So now is the time for America not to think just of yesterday or not just of tomorrow, but to think of generations yet unborn, so that we can prepare this society for them and leave it a society that is a glorious society that we can be proud of and that the historians will point to as a development that is unheard of in any nation.
Context
Remarks to a Group in Connection With the Montana Territorial Centennial.
04/16/1964