* New archives open up. Western scholars did not have access to archives within the Soviet Union during the Cold War, but this changed after 1991. Allowing access to historical documents heretofore unseen naturally led to new historical interpretations.
* Individuals donate their family collections to local historical societies. While I would imagine that the overwhelming majority of these sources are quotidian and uninteresting, occasionally they are not and we come across treasure troves.
* Analytical paradigms come in and out of fashion. Before roughly the 1960s, few professional historians had examined the history of non-elite, ordinary individuals; history from the "bottom up" so to speak. Social history began to dominate in the 1970s but has declined somewhat since then. Meanwhile, only in the last few decades have women, non-white, and LGBT historians added to the ranks of the profession. In my own sub-field the paradigms of "republicanism" and the "market revolution" were once popular, but ceased to be so after the 1990s. With the 2008 recession, the "history of capitalism" gained popularity.
* New digital tools enable new techniques, new interpretations, and the ability to answer new questions. This is ongoing.
* Intelligence agencies can release information that had previously been classified. When I first learned about the Gulf of Tonkin "incident" in high school, I learned that we should be skeptical and that an attack may not have occurred. Now we know definitively that an attack did not take place.
* The passage of time changes our perspective on historical events. Sometimes things that seemed like a really big deal at the time have not endured in their significance, and sometimes the opposite is true. Growing up in the Bay Area in the 1990s, amidst a Silicon Valley boom that was literally creating an entire middle class, I remembered life fondly. I remembered thinking that Bill Clinton was a good president. Now I am not so sure. The 2008 financial crisis, which was caused at least partially by financial deregulation, which Clinton enabled by repealing Glass-Steagall, gave me a different perspective on the 1990s. The same was true of NAFTA, a punitive crime bill, and welfare reform.
* Rediscovery. Sometimes we need historians to help us remember lessons or themes that, as a nation, we seem to have forgotten, either deliberately because it suits some political agenda, or innocently because of the passage of time. In this post-WWII era where too many Americans associate the US military with spreading "freedom" (rather than imperialism?), we have to remind ourselves that the Founding Fathers, steeped in notions of traditional English liberty, regarded a standing military as anathema to freedom. What else explains the colonists' opposition to quartering troops and the Third Amendment to the Constitution? What else but a historian can remind us that civil rights, the creation of our national parks, social security, Medicare, the Homestead Act, the Transcontinental Railroad Act, the National Reclamation Act, and sundry other pieces of legislation, demonstrate the advantages of using the power of government in our economy? As historian Brian Balogh argued, we have a "collective amnesia" about the role of government in society due, in no small part, because of a religious, unquestioning, Reaganite devotion to "free markets."
* Archaeologists and anthropologists can make new discoveries that lead us to change how we write the history of pre-Columbian peoples, including the peopling of North America, which is usually the first lecture and textbook chapter in a college-level survey of US history.
* Historians can re-examine old topics and write about them in new ways
* Current events. As someone who loves news and politics but is a professional historian by trade, I'm always thinking about this. The examples are limitless. A historian writing in the 1980s would naturally write differently about Pearl Harbor compared to a historian writing in a post-9/11 world. This is not only because 9/11 ushered in a frightening, dystopian world of pseudo-patriotism, fear-mongering politics, ill-conceived military invasions, torture, spying, racism, and an enlarged national security state willing to abuse civil liberties, but as an attack on US soil, the event forced historians to look back to other times in which the country had been attacked. Dylan Roof's massacre of African American churchgoers in Charleston, South Carolina made us look less sympathetically toward the Confederate flag (and there wasn't that much sympathy in the first place). The Confederate flag, long a symbol of "heritage" and "states' rights" among white southerners of a certain class, background, and political persuasion, was removed by Republican Governor Nikki Haley.
Today I write during a heated election season in which the bombastic and racist demagogue, Donald Trump, has taken almost everyone by surprise in securing the Republican Party nomination. While it is easy to say that his candidacy has come out of nowhere, the historian knows better. The historian knows that any complex event has a historical context.
The Trump candidacy proves a lot of things. It would take an entirely separate blog entry, and a long one at that, to go over how insane, irrational, insecure, and dangerous Donald Trump is, but let's take it as a given at the moment. Because it's impossible for historians to be "objective," not the least of which because we're always influenced by the current environment and events in which we live, the rise of Trump should force self-reflection and introspection among Republicans and non-Republicans alike. This includes looking back to the past. Is Trump's candidacy an aberration? Or is it just a more extreme variation of a trend that has been building for decades? One thing is abundantly clear: Trump's rise proves that Republican Party base voters don't care at all about the details of governing or policy; they care about being angry merely for the sake of being angry. They care about personality and they value fake, outlandish expressions of masculinity, sexism, and racism. Just look at how the poll numbers shot up after every ill-conceived, childish, and bombastic statement statement uttered from the mouth of Donald Trump:
All of this is to say that the discipline of history is never truly settled. It is constantly evolving. It is constructed. It is almost always open to reinterpretation, debate, contested meanings, and especially, a whole lifetime of fun and enriching conversation!