A Case for Memoirs
It is often the case in the historical profession to shun memoirs in favor of evidence deemed closer to the events like letters, diaries, affidavits, newspaper articles, and other documents. Indeed, as an undergrad, I recall being told that memoirs were a horrible source that was to be avoided at all costs. All memoirs were, I was told, was someone trying to exaggerate their importance during a historical moment. At the time, that was was probably good advice for an untrained undergrad working on their first paper using primary sources. But now as someone who has earned a PhD in history I cannot avoid memoirs. In fact, memoirs are some of my most prized possessions and are a source I work with closely in all of my work.
REASON 1: CHANGE OVER TIME
One of the reasons I love memoirs is that the author will often deliver some observation of change over time that is worth further study. I am an environmental historian and what some folks view as throwaway lines are gold for my work. Some might say that certain plants or animals were far more plentiful in their youth than today. This is especially true of animals like the bison on the late 19th century Great Plains, the region at the heart of my dissertation. We see in the eyes of the memoirist, meaningful changes over the course of their lives that are worth tracking and unpacking.
REASON 2: LEARNING
Sometimes, the author of a memoir will admit their fault in something profound. They will say, that in the moment they thought one thing, but experience has taught them that the opposite was true. Now that is the exact opposite of what I was cautioned about in undergrad. Of course it may be the exception, but when this learning is present it helps the historian as well.
REASON 3: THE POST MORTEM TELL ALL
Some folks, especially those engaged in covert or criminal activity, keep their cards close and leave few documents behind. However, in old age, some of those people give candid explanations for actions that simply confuse historians attempting to interpret an event. Many historians need to find the smoking gun that proves their theory about a particular moment and they never find it. But, a chance glance at a memoir might be all they need to confirm their suspicion.
REASON 4: SOMETIMES ITS THE ONLY OPTION
One of the hardest parts about being a historian is that not everyone produces documents, or at least, the documents you wish they would. Not everyone is literate. But, sometimes a literate person finds them in their old age, says something to the effect of, “Hey, you lived through X? Can you tell me your story?” And suddenly there is an as told to memoir in the making. Such works became popular in the early 20th century.
There is then, a case for memoirs. Do not discard them. They provide valuable insights, hold long kept secrets, and sometimes they are the only source you will get. The warning from undergrad might remain in a changed form. Use them, but use them wisely.

Facts are facts. The astute and brave historian follows facts.