A digital print of an entry from the diary of William Still, an African American abolitionist, 1821-1902.
"The Negro Moses". The Columbian (Bloomsburg, PA), July 8, 1897 Page 2, Image 2. col. 3.
Secondary Sources:
The Abolitionist Movement by Claudine L. Ferrell, published by Greenwood Publishing, 2006.
"Harriet Tubman and the Underground Railroad" (an article retrieved from nps.gov.March 11, 2017).
A primary source is one that contains original first-hand information about the subject under study. As such, it is usually written around the same time the event or subject happened.
The subject here is Harriet Tubman who lived from 1820 to 1913 which means that any primary source about her would have to have been written within that time period.
A secondary source for the purpose of this question, would be one that was written after 1913.