Final answer:
Obama's inaugural address is classified as a primary source because it is an original, unaltered document and firsthand account of an event. Such sources are direct evidence and contrast with secondary sources that analyze and interpret primary materials.
Step-by-step explanation:
When considering the nature of Obama's inaugural address in the context of United States history, we classify this document as a primary source. A primary source is an original document or firsthand account of an event that hasn't been altered or interpreted by later historians or writers. Examples of primary sources include speeches, letters, diaries, news footage, interviews, and official records, among others. In contrast, secondary sources consist of analyses, summaries, or interpretations of primary sources.
For instance, if you were looking at James Monroe's inaugural address or Abraham Lincoln's inaugural address, these original speeches are primary sources because they provide direct evidence about the historic events they describe. Other examples include David Walker's Appeal and 30 Years a Slave as they represent unmediated accounts of their respective author's experiences and viewpoints. Conversely, a textbook entry about the battles of the Civil War or a website analyzing themes in John F. Kennedy's inauguration speech would be secondary sources since they interpret and discuss primary documents.