The most common primary sources are written documents, but they may also include photographs, paintings, sculptures, architecture, oral interviews, statistical tables, and even geography. While nearly all the cloths, fabric, and jewelry from Ancient Inca and Aztec times have been destroyed, we can obtain an idea of the history of fashion by looking at paintings left over from those years. Interviews may be the most powerful primary sources. If you are writing about a particular Civil Rights Movement during the 1960s, don't rely entirely on newspaper accounts or on books about the movement. Find some participants and ask them as many questions as you can.
Primary sources are the most powerful resources when researching a topic.
The more primary sources one can obtain, the stronger the piece of writing shall be. The secondary sources for the essay written about Abraham Lincoln would include books and articles written about him by various authors. Secondary sources are extremely helpful when you are in need of another persons opinion and may contain good information, but are a weaker source than a primary source. They are extremely helpful when you are in need of another persons opinion.