As you begin assessing evidence in a source, determine whether you are reading a primary or a secondary source.
Primary sources are original documents such as letters, diaries, legislative bills, laboratory studies, field research reports, and eyewitness accounts.
Secondary sources are commentaries on primary sources—another source’s opinions about or interpretation of a primary source.
Although a primary source is not necessarily more reliable than a secondary source, it has the advantage of being a firsthand account. Naturally, you can better evaluate what a secondary source says if you have first read any primary sources it discusses.
A primary source for Ned Bishop was Nathan Bedford Forrest’s official report on the battle at Fort Pillow. Bishop also consulted a number of secondary sources, some of which relied heavily on primary sources such as letters.