For this assignment, you've been asked to do research on your chosen speech from the Voices of Democracy website: "In addition to the interpretative essay that accompanies your chosen speech, please research 5 additional sources that provide information on the context, the social movement, the speech’s impact, and/or the communication strategies employed." (from the assignment description but emphases mine).
For broad background on social movements, try one of these catalog subject headings:
Social movements > United States
Or, look for the subject heading related to specific movements or causes, for example:
Use this handout to help you know how to track down sources from citations you find in bibliographies: